First came the push mowers, then power mowers, and now there are robotic mowers that let you put your feet up.

Consumer Reports' lawn-care expert Peter Sawchuk tested two. They don't come cheap:
Friendly Robotics RL 1000 RoboMower costs $2,000
LawnBott's LB 3200 Evolution cost $2,500

Testers found a safety problem with the LawnBott that could injure an adult or curious child.

"When you lift this up, the blade keeps spinning" said Sawchuk. "You can easily reach in and get a nasty injury. If you lift it up further, the blade will stop, but it takes several seconds."

The RoboMower doesn't have that safety problem. Lift it up just a little and the blades stop quickly.

The RoboMower is designed to work several hours every day or two, trimming off a little bit of grass as it moves about in a random pattern.

To keep it in your yard the RoboMower is supposed to turn around when it reaches a wire you lay around the perimeter. And it's supposed to go to a home base for a recharge once its battery runs down.

But Peter says you can't just start the RoboMower and forget it.

"We found that there were times when it just stopped dead and it actually had to be picked up and physically returned to its charging station" said Sawchuk. "There were other times that the RoboMower went outside its perimeter wire and we had to chase it down."

Peter says all in all a regular mower does a better job and is a whole lot cheaper.

A spokesperson for the US distributor for the LawnBott told Consumer Reports there is a software update for the LawnBott 3200 Evolution so the blade stops within a second after it's lifted about 35-degrees. But Consumer Reports says even with that change, the robotic mower poses as serious risk. Consumer Reports has reported the problem to the Consumer Product Safety Commission.