The LawnBott may look like Arnold Schwarznegger's cycling helmet, but it's actually a cordless, remote-controlled lawnmower with a flat blade that mulches the grass as it cuts it. Charge it up on its docking station and it will go for 4 hours—or 33,000 square feet—on one single charge. It's apparently so quiet that you can let it run all night without bugging the neighbors, it doesn't mind a bit of light rain, and a heavier shower will send it toddling back to its base station like the obedient little robot it is.
It does hills—anything up to a 1:4 gradient, in fact—and only uses around $7 to $10 of electricity each year. The downside is the price: the LB2000 Professional will set you back $1,749.