This R/C Moon Hack is a great example of taking an existing product, adding some electronics and enhancing the functionality of the device. By adding a microcontroller and a realtime clock this R/C moon display now shows the actual moon phase with no user intervention.
"I first saw this R/C Moon Phase light at ThinkGeek some time ago and decided it would be ripe for hacking. Essentially, the R/C Moon Phase light is a nightlight that comes bundled with an infrared remote control. The controller allows the user to change the moon’s current phase with the press of a button – or automatically cycle through the standard phases of the moon (ie. waning crescent, waxing crescent, full, etc…) which it accomplishes with six LED’s and an impressively designed outer shell. I decided that it would be more interesting if the model moon actually reflected the current phase of the moon based on the current date. Using an arduino and a DS1307 realtime clock module from Sparkfun, I was able to make that it do just that. The DS1307 module contains a coin cell battery backup that enables the internal clock to maintain the proper time, even without power, for up to 17 years!"