Check out the Robocut, a lawnmower robot with Basic Stamp as controller. You can even buy the kit so you can build one yourself.
Now, if you can get one of these DIY kits and make it solar, that’d be something to watch.
“RoboCut, is a BASIC Stamp powered robot. Two 12Volt motors with gearbox gives the two large drivewheels good traction and the robot can manouver in very small areas. Powersource is a NiMh accu-pack at 12V, 4.1 Ah. One motor gives the cutterdisk a rpm at approx. 3500 rpm. A Basic STAMP 2 is the brain in the PCB mounted in the front of the Robocut. This PCB has the following features. -Two-chanel (right/left) Buried Wire Fence (BWF) detectors. -Two-chanel (right/left) active IR obstacle detection -Two chanel (right/left) drive motor control on/off, Forward/Rewerse -One chanel cutter-motor control on/off, MOS-FET 20 Amp -Charging/accuvoltage measuring with high resolution -Charger detection On/off -Optional temperature sensor to check accupack temp during charging. -prototype area -prepared for optional “self-charging” and navigating to the chargingstation via an IR_beacon.”