To stop your app from timing out and going to sleep you can use:
[UIApplication sharedApplication].idleTimerDisabled = YES;
This will, obviously, disable the idle timer and stop your iphone from automatically going into sleep mode.
Edit: As middaparka stated you should re-enable the idle timer when you no longer need to keep the phone awake (generally after that view has been removed) using:
[UIApplication sharedApplication].idleTimerDisabled = NO;
Cheers