Swift 2

import UIKit

extension UIDevice {

    var modelName: String {
        var systemInfo = utsname()
        uname(&systemInfo)
        let machineMirror = Mirror(reflecting: systemInfo.machine)
        let identifier = machineMirror.children.reduce("") { identifier, element in
            guard let value = element.value as? Int8 where value != 0 else { return identifier }
            return identifier + String(UnicodeScalar(UInt8(value)))
        }
    
        switch identifier {
        case "iPod5,1":                                 return "iPod Touch 5"
        case "iPod7,1":                                 return "iPod Touch 6"
        case "iPhone3,1", "iPhone3,2", "iPhone3,3":     return "iPhone 4"
        case "iPhone4,1":                               return "iPhone 4s"
        case "iPhone5,1", "iPhone5,2":                  return "iPhone 5"
        case "iPhone5,3", "iPhone5,4":                  return "iPhone 5c"
        case "iPhone6,1", "iPhone6,2":                  return "iPhone 5s"
        case "iPhone7,2":                               return "iPhone 6"
        case "iPhone7,1":                               return "iPhone 6 Plus"
        case "iPhone8,1":                               return "iPhone 6s"
        case "iPhone8,2":                               return "iPhone 6s Plus"
        case "iPhone9,1", "iPhone9,3":                  return "iPhone 7"
        case "iPhone9,2", "iPhone9,4":                  return "iPhone 7 Plus"
        case "iPhone8,4":                               return "iPhone SE"
        case "iPad2,1", "iPad2,2", "iPad2,3", "iPad2,4":return "iPad 2"
        case "iPad3,1", "iPad3,2", "iPad3,3":           return "iPad 3"
        case "iPad3,4", "iPad3,5", "iPad3,6":           return "iPad 4"
        case "iPad4,1", "iPad4,2", "iPad4,3":           return "iPad Air"
        case "iPad5,3", "iPad5,4":                      return "iPad Air 2"
        case "iPad2,5", "iPad2,6", "iPad2,7":           return "iPad Mini"
        case "iPad4,4", "iPad4,5", "iPad4,6":           return "iPad Mini 2"
        case "iPad4,7", "iPad4,8", "iPad4,9":           return "iPad Mini 3"
        case "iPad5,1", "iPad5,2":                      return "iPad Mini 4"
        case "iPad6,3", "iPad6,4", "iPad6,7", "iPad6,8":return "iPad Pro"
        case "AppleTV5,3":                              return "Apple TV"
        case "i386", "x86_64":                          return "Simulator"
        default:                                        return identifier
        }
    }
}

if UIDevice.currentDevice().modelName == "iPhone 6 Plus" {
    // is an iPhone 6 Plus
}

Swift 3

import UIKit

public extension UIDevice {

    var modelName: String {
        var systemInfo = utsname()
        uname(&systemInfo)
        let machineMirror = Mirror(reflecting: systemInfo.machine)
        let identifier = machineMirror.children.reduce("") { identifier, element in
            guard let value = element.value as? Int8 , value != 0 else { return identifier     }
            return identifier + String(UnicodeScalar(UInt8(value)))
        }

        switch identifier {
        case "iPod5,1":                                 return "iPod Touch 5"
        case "iPod7,1":                                 return "iPod Touch 6"
        case "iPhone3,1", "iPhone3,2", "iPhone3,3":     return "iPhone 4"
        case "iPhone4,1":                               return "iPhone 4s"
        case "iPhone5,1", "iPhone5,2":                  return "iPhone 5"
        case "iPhone5,3", "iPhone5,4":                  return "iPhone 5c"
        case "iPhone6,1", "iPhone6,2":                  return "iPhone 5s"
        case "iPhone7,2":                               return "iPhone 6"
        case "iPhone7,1":                               return "iPhone 6 Plus"
        case "iPhone8,1":                               return "iPhone 6s"
        case "iPhone8,2":                               return "iPhone 6s Plus"
        case "iPhone9,1", "iPhone9,3":                  return "iPhone 7"
        case "iPhone9,2", "iPhone9,4":                  return "iPhone 7 Plus"
        case "iPhone8,4":                               return "iPhone SE"
        case "iPad2,1", "iPad2,2", "iPad2,3", "iPad2,4":return "iPad 2"
        case "iPad3,1", "iPad3,2", "iPad3,3":           return "iPad 3"
        case "iPad3,4", "iPad3,5", "iPad3,6":           return "iPad 4"
        case "iPad4,1", "iPad4,2", "iPad4,3":           return "iPad Air"
        case "iPad5,3", "iPad5,4":                      return "iPad Air 2"
        case "iPad2,5", "iPad2,6", "iPad2,7":           return "iPad Mini"
        case "iPad4,4", "iPad4,5", "iPad4,6":           return "iPad Mini 2"
        case "iPad4,7", "iPad4,8", "iPad4,9":           return "iPad Mini 3"
        case "iPad5,1", "iPad5,2":                      return "iPad Mini 4"
        case "iPad6,3", "iPad6,4", "iPad6,7", "iPad6,8":return "iPad Pro"
        case "AppleTV5,3":                              return "Apple TV"
        case "i386", "x86_64":                          return "Simulator"
        default:                                        return identifier
        }
    }
}

if UIDevice.current.modelName == "iPhone 7" {
    // is an iPhone 7
}

override func viewDidLoad() {
    super.viewDidLoad()
    NotificationCenter.default.addObserver(self, selector: Selector(("batteryStateDidChange:")), name: NSNotification.Name.UIDeviceBatteryStateDidChange, object: nil)
    NotificationCenter.default.addObserver(self, selector: Selector(("batteryLevelDidChange:")), name: NSNotification.Name.UIDeviceBatteryLevelDidChange, object: nil)

    // Stuff...
}

func batteryStateDidChange(notification: NSNotification){
    // The stage did change: plugged, unplugged, full charge...
}

func batteryLevelDidChange(notification: NSNotification){
    
    let batteryLevel = UIDevice.current.batteryLevel
    if batteryLevel < 0.0 {
        print(" -1.0 means battery state is UIDeviceBatteryStateUnknown")
        return
    }
    
    print("Battery Level : \(batteryLevel * 100)%")
    // The battery's level did change (98%, 99%, ...)
}

 UIDevice *deviceInfo = [UIDevice currentDevice];
 NSLog(@"Device Name %@", deviceInfo.name);
 //Ex: myIphone6s
 NSLog(@"System Name %@", deviceInfo.systemName);
 //Device Name iPhone OS
 NSLog(@"System Version %@", deviceInfo.systemVersion);
 //System Version 9.3
 NSLog(@"Model %@", deviceInfo.model);
 //Model iPhone
 NSLog(@"Localized Model %@", deviceInfo.localizedModel);
 //Localized Model iPhone
 int device=deviceInfo.userInterfaceIdiom;
 //UIUserInterfaceIdiomPhone=0
 //UIUserInterfaceIdiomPad=1
 //UIUserInterfaceIdiomTV=2
 //UIUserInterfaceIdiomCarPlay=3
 //UIUserInterfaceIdiomUnspecified=-1
 NSLog(@"identifierForVendor %@", deviceInfo.identifierForVendor);
 //identifierForVendor <__NSConcreteUUID 0x7a10ae20> 556395DC-0EB4-4FD5-BC7E-B16F612ECC6D

UIDevice *deviceInfo = [UIDevice currentDevice];
int d = deviceInfo.orientation;

deviceInfo.orientation returns an UIDeviceOrientation value which is shown as below:

UIDeviceOrientationUnknown 0
UIDeviceOrientationPortrait 1
UIDeviceOrientationPortraitUpsideDown 2
UIDeviceOrientationLandscapeLeft 3
UIDeviceOrientationLandscapeRight 4
UIDeviceOrientationFaceUp 5
UIDeviceOrientationFaceDown 6

Listening for device orientation changes in a View Controller:

- (void)viewWillAppear:(BOOL)animated
{
    [super viewWillAppear:animated];
    [[UIDevice currentDevice] beginGeneratingDeviceOrientationNotifications];
    [[NSNotificationCenter defaultCenter] addObserver:self 
                                             selector:@selector(deviceOrientationDidChange) 
                                                 name:UIDeviceOrientationDidChangeNotification
                                               object:nil];
}

-(void)deviceOrientationDidChange
{
    UIDeviceOrientation orientation = [[UIDevice currentDevice] orientation];
    if (orientation == UIDeviceOrientationPortrait || orientation == UIDeviceOrientationPortraitUpsideDown) {
         [self changedToPortrait];
    } else if (orientation == UIDeviceOrientationLandscapeLeft || orientation == UIDeviceOrientationLandscapeRight) {
         [self changedToLandscape];
    }

-(void)changedToPortrait
{
    // Function Body
}

-(void)changedToLandscape
{
    // Function Body
}

To disable checking for any orientation change:

- (void)viewWillDisappear:(BOOL)animated {
    [super viewWillDisappear:animated];
    [[UIDevice currentDevice] endGeneratingDeviceOrientationNotifications];
}

//Get permission for Battery Monitoring
[[UIDevice currentDevice] setBatteryMonitoringEnabled:YES];
UIDevice *myDevice = [UIDevice currentDevice];

[myDevice setBatteryMonitoringEnabled:YES];
double batLeft = (float)[myDevice batteryLevel] * 100;
NSLog(@"%.f",batLeft);

int d = myDevice.batteryState;
//Returns an Integer Value 
//UIDeviceBatteryStateUnknown 0
//UIDeviceBatteryStateUnplugged 1
//UIDeviceBatteryStateCharging 2
//UIDeviceBatteryStateFull 3

//Using notifications for Battery Monitoring
-(void)startMonitoringForBatteryChanges
{
// Enable monitoring of battery status
[[UIDevice currentDevice] setBatteryMonitoringEnabled:YES];
// Request to be notified when battery charge or state changes
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(checkBatteryStatus) name:UIDeviceBatteryLevelDidChangeNotification object:nil];
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(checkBatteryStatus) name:UIDeviceBatteryStateDidChangeNotification object:nil];
}
-(void) checkBatteryStatus
{
NSLog (@"Battery Level is %.f",[[UIDevice currentDevice] batteryLevel]*100);
 int d=[[UIDevice currentDevice] batteryState];
    if (d==0)
    {
        NSLog(@"Unknown");
    }
    else if (d==1)
    {
        NSLog(@"Unplugged");
    }
    else if (d==2)
    {
        NSLog(@"Charging");
    }
    else if (d==3)
    {
        NSLog(@"Battery Full");
    }
}

//Enabling the proximity Sensor
- (void)viewWillAppear:(BOOL)animated {

    [super viewWillAppear:animated];
    [[UIDevice currentDevice] setProximityMonitoringEnabled:YES];
    [[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(sensorStateMonitor:) name:@"UIDeviceProximityStateDidChangeNotification" object:nil];
}

- (void)sensorStateMonitor:(NSNotificationCenter *)notification
{
    if ([[UIDevice currentDevice] proximityState] == YES)
    {
        NSLog(@"Device is close to user.");
    }

    else
    { 
        NSLog(@"Device is not closer to user.");
    }
}