Add the following line of code to stop the iPhone from going to sleep mode. (Use it judiciously, it will drain the device battery.)

[[ UIApplication sharedApplication ] setIdleTimerDisabled: YES ];
About Me: Anish Kumar:
Mac OS X software development is my bread winner with over 6 years of experience. Expertise in Color Management, TWAIN Scanner drivers on Mac OS X, Photoshop Filter and Import Plugin development on Mac OS X, iPhone. As an hobby I love to work on PHP, Flex, AIR, Photoshop. Check the 'About' page for more.