These $77 PicoBotz kits are the perfect thing to let the budding engineer (your kids) get their hands on some robotics. The "robot" has 180 programmable commands and operates in three modes, obstacle avoidance, sound repositioning mode, and line tracing mode.
It also runs on two AA batteries, just like the Cylons from Battlestar Galactica. It's also a good thing these bots have their "kill all humans and enslave humanity" mode removed. That first version didn't sell so well. [Scientifics Online via MAKE via Slashgear via Uber Gizmo]