Hows this for an idea - a small metal ball (maybe 1' x 1') with spikes (2-7" each) to plow your yard for you (think of the agricultural purposes!) that runs off of solar energy! You can put a chip into it that makes it run for a certain distance (say, 100 meters), turn about a foot, and come back, then repeat until you use a remote to click it off! You can even put seeds in a container inside and have it automatically plant them at whatever distance you tell it to (retractable/extendable...