This app definitely does what it claims, but its an impractical application of the idea. The real problem is the camera and the cameras perspective. Sitting in a dock, etc. -- unless set with plenty of space between device and background -- the image behind the clock will likely be blurred, or just a different enough perspective to break the "see-through" illusion, or just uninteresting. Neat idea... but save your 99¢.
afluke about Chameleon Clock