The Arc Mouse from Microsoft is an affordable, battery-powered mouse that folds up for portability. Unfortunately, I recently lost the little USB dongle that came with mine, rendering it useless. I've seen the inside of a mouse before, but was intrigued by the fact that you can turn this one off just by folding it, so I took it apart to find out how it works.
We use Test Indicators all the time at Other Machine Co; whether it's during incoming part inspection or during final QA, they get a lot of use. Unfortunately, we recently had a casualty, and I was able to bring it home and tear it down.