If you want to buy a phone, this is the app to check for stuck pixels. Or if you already have them, you can try to fix them now. Using the three most popular methods of fixing dead pixels, Dead Pixel Fixer will try it's best to fix your screen, and it's been proven to work with 3 out of 4 broken pixels. Update: improved speed! (greatly affects the app's ability to fix stuck pixels)

Dead Pixel Fixer screenshots: