SirNickity:
On the topic of mechanized lawn-care, I recently acquired an old robo-mower that I can lobotomize. I have no plans for dandelion picking, but I'm keen on any discussion regarding boundary navigation.
Don't know what you have, but I have a old Friendly Robotics RL-500 sitting in my garage waiting for its lobotomy; I didn't want to deal with the boundary wire, either. My idea for the boundary detection is to mount (using epoxy) small magnets to golfball tees, and stick those around the boundary about every 6-8 inches or so. Then use hall-effect sensors to detect them. The greater problem I am wondering about is detecting cut grass from uncut grass (a high-speed humidity sensor might work); I don't want to run the blades constantly, and I want to detect (and map) where it's been cut already.