A computer mouse is typically an input device. Add a few motors, switches, and batteries, and as seen in this hack by Tony K, you have something that moves around on the floor by itself. It’s even able to deal with obstacles thanks to its switch/whisker setup, which enables it to back up slightly and turn after making contact.
The device is brilliantly simple, using each switch to control the motors directly for tank-like differential steering. A battery pack provides power, and the motors are mounted at 45º via hot glue along with cardboard supports to allow for ground contact. To increase friction when spinning, pieces of heat shrink tubing are attached to the motor shafts.
It’s quite the clever little “pet,” which Tony notes would take much less effort to take care of than an actual pet (or… not pet mouse) mouse. What it lacks in computing power–no microcontroller or even anything more advanced than a microswitch – it makes up for in style. The former interface cable now acts as a tail, and googly eyes supplement its microswitch whiskers.
On the other hand, this former-mouse concept is just asking to be more fully automated. One could see a microcontroller and transistor/motor driver integrated for onboard control, and maybe even some sort of remote RF interface. Perhaps old unused computer mice (especially oversized models) should be on the lookout for parts-seeking predators!