Glow-in-the-dark

[embed]http://www.youtube.com/watch?v=nLy64hMeLrg[/embed]

It's quite simple. It uses an MSP430G series micro-controller and an LDR for detecting light intensity. The detection is translated into interrupts with the analog comparator in the MCU. The special point about this is that it consumes really low power, thanks to the low power MSP430 micro-controllers from TI. It's running on two AA alkaline batteries for nearly a month with being always powered on standard day night cycles.