I believe Dennis is using the wrong terminology. Scanning and mapping your surroundings isn't GPS, they just use rangefinders. Really, there is no reason the technology couldn't be used in these situations as well. I mean, it's been used in demos for a robot to deliver a pizza a few blocks away, all the while avoiding people along it's route as well as "simple" tasks as delivering a can of pop from across the room while avoiding couches and pets.
Now, I'm not saying it isn't a great idea, but from my experience (LB3200), these guys have a hard enough time building something reliable at all, not including all the real "techie" gadgets that could be used. I posted (other forum) in the past how easy it would be to use an accelerometer (including data/graphs) to detect when the bot is stuck so they could do infinite smart spirals and the like. Cost to add an accelerometer? Around $5, not including the multiple years of engineering it would take for them to get it right.

One of the problems I have, is if you break down the real technology inside of one of these things, I just can't seem to figure out how to justify the $3,000 price tag. Don't get me wrong, I'd do it again in a heart beat and it's worth twice that in my opinion (if it didn't break down so easy). But, look at the hardware in a Nintendo Wii for example (on the techie side of things). And it's $200. For the mechanical side of things, look at your standard electric power mower. You can pick one up for $300. So, if you could marry those two, you'd still have $2,500 left over for robotic mowing specifics. And if you look at the programming involved with the current models.. they are pretty darn dumb. You could reproduce it with a $260 Lego mind-storms kit.
Sorry for the "rant".