This app allows you to compare two pictures with each other. Just make a photo of the images or load stored pictures and hit the compare button. The two pics will then be alternately displayed which makes it pretty easy to see the differences. Once you made the first picture, it will be presented as an overlay when you take the other one. This way you can be sure that the two photos cover the same area. You can save the pictures too. Internet is needed for ads only. I've tested it on an HTC Desire, HTC Desire HD, Samsung Galaxy S and Motorola Droid/Milestone.