Of the 100 home automation techniques in Smart Home Hacks, the discussion of Doug Smith's method for building an inexpensive robotic lawn mower generated a lot of raised eyebrows. It's crazy, it's clever, and yes it actually works.
Doug recently let me know that he's posted video of his experiment, along with some updates. See Lazy Lawn Mowing for details. You'll also find a link to Doug's RoboMowerWiki, where you can learn much more refined, and safer, techniques.