For iPhone and iPad. Available in the App Store for 99 cents. Uses the device’s camera to display a seemingly transparent background.
Get Chameleon Clock in the iTunes App Store.
I could be wrong, but I feel like you’d have to get it set up and zoomed in juuuuust right, PLUS be looking at it at the perfect angle in order for the transparency to look legit. Your best bet would be to have a dock set up in your bedroom or office such that those variables could easily stay constant once you get your placement and set-up perfected.