THX Ltd. has THX tune-up (iTunes Link) for the iPhone, iPod Touch, and iPad in the iTunes App Store for FREE (regularly $1.99) for a limited time.

THX tune-up  allows you to properly adjust your TV, projector and speakers, helping you get the most out of your entertainment system.

THX tune-up features custom video test patterns, carefully selected photos and tutorials to help you adjust and confirm the best picture settings on your display based on your room lighting. Using special test sounds, THX tune-up also lets you check your external speakers to make sure they are working in phase and are connected properly for 2-channel stereo or 5.1 surround sound systems.

THX tune-up is completely interactive — go through it at your own pace, in any order. Connect a supported iOS device to the display or sound system with an HDMI adapter & cable, or via AirPlay with Apple TV (3rd gen).

To get started, locate the adjustment buttons on your television and audio video receiver (AVR) remote controls and then simply follow the THX app tutorials which will walk you through your “THX tune-up.” The app offers tips about your remote control, room lighting, viewing distance and other helpful advice.