With everyone hacking into the new PowerBook bump sensors —
accelerometers built into the PB to protect the HD if you drop it — it
was only a matter of time before someone figured out a way to control
music by tilting. Bumptunes is a script that lets you, um, tilt, rock, bump, or otherwise abuse your laptop to advance to the next track. (via PowerPage)

Why stop there? How about adding accelerometers to your keyboards
(QWERTY or music), your mouse . . . the possibilities are limitless.

Okay, not quite limitless, but, well, quite a bit of gear-beating fun.