There are days when you probably do want to thump your computer. But what if you could use that anger to actually power it on?
This is the idea behind this nifty little hack, which uses a small sensor to emulate a PS/2 device connected to a PC that can take PS/2 input as a signal to boot. It's not entirely a casual hack, although with listed pricing at around $US10 in parts, it's not exactly expensive, either.
Turn a PC on with a Knock and an ATTiny [Hack A Day]