The Dharma Initiative hatch clock reproduces the countdown clock from the second season of Lost, complete with sound effects and a terminal to type the numbers into to reset it. For the full experience, you can even set it to disable system sleep, so you really do have to “press the button” every 108 minutes (although as far as I can tell it doesn’t actually do anything dreadful if you let it run down!)
Utterly pointless, but nicely implemented and strangely compelling.
[Update] It does become slightly less compelling when you accidentally shut a cat in the room, it walks over the keyboard waking the machine from sleep, and you get woken at 4.30 AM by the “one minute to go” klaxon.