gistfile1.m

UIDevice *myIphone=[UIDevice currentDevice];

myIphone.batteryMonitoringEnabled=YES;

float level=myIphone.batteryLevel;
UIDeviceBatteryState state = myIphone.batteryState;

myIphone.batteryMonitoringEnabled=NO;

NSString *statusText=@"";

switch (state) {
    case UIDeviceBatteryStateUnknown:
        statusText=@"status unknown";
    case UIDeviceBatteryStateUnplugged:
        statusText=@"iPhone unplugged";
    case UIDeviceBatteryStateCharging:
        statusText=@"battery charging";
    case UIDeviceBatteryStateFull:
        statusText=@"battery full";
}

NSLog(@"Battery level: %f (%@)", level, statusText);