This is the LawnBott by Kyodo. I've had a lot of fun trying it out on my grass. A perimeter wire is set up around the lawn which is hooked to a transmitter. The LawnBott will cut the grass inside the perimeter. It's lightweight, has lots of safety features and will climb a slope too.
It has a docking station that it will find after completing its work and will automatically recharge. The robot can be programmed to cut the grass as often as you would like. It can also be adjusted to cut the grass at your preferred length.
I'll continue testing it out, for now you can see a demonstration video in the player to the right.