Pixel Checkup is a free and simple yet useful app for Windows Phone 7 users that allows the users to find dead pixels. The app fills the screen with different colors notably white, black, red, green, blue or alternating colors which makes it easier to notice dead / stuck pixels which may only be visible when a certain color is displayed.

Once you identify the dead pixel, you can mark the spot using the pins. The pins are available even after you change the colors.