If you have a good sense of balance, you can ride a unicycle or get on TV doing tricks with ladders. We don’t know if [Hanna Yatco] has a good sense of balance or not, but we do know her Arduino does.

The HC-SR04 sonar modules are available for a mere pittance and, with some coaxing, can do a pretty decent job of helping your robot measure the distance to the nearest wall. But when sellers on eBay ...