I've been following the project for a year now and Clemens Elflein has actually managed to get the topic off the ground professionally. Recently, his kit is available, with which you can upgrade a cheap Yardforce robotic mower to GPS support. This eliminates the need to lay boundary wires.
I've been following this for a while because even though I have a small lawn, lawncare is easily one of my least favorite activities.
I also would suggest thi8s gets reposted to other tool/gardening/homeowner related subs too.