Recently I had trouble with my iPod touch thinking my headphones were still plugged in when they werent, and thus no sound would come out of the speakers. I searched the Internet for a solution but found only random off-the-cuff answers that didnt work for me. Though hundreds had the problem, the official site never addressed it. Phone Doctor can test the external hardware on your device, and I tested the speakers, headphone jack and the internal headphone sensor, and using that information was able to fix the problem. It has tests for everything, and in addition just reminded me that I could save power by turning off my location service, when I didnt even know it was on! (No indicator at the top whatsoever). So this app does a lot of crucial things, and it does them very well. No iPhone/iPod owner should be without it.