"Active bumper" electromechanical technology has been around for years, embodied as it is in pinball machines (link). The Roomba is an iRobot corporation (link) product that sits around waiting for an opportunity to sweep up your floors, when it springs to life. Dogs chase ball to the point of exhaustion or until the ball rolls under a couch.
My hypothesis is that a dog would totally exhaust itself if its humans would be so good as to crawl under the furniture and retrieve doggy the ball. Humans, though, have an aversion to excercise and particularly the crawl most noticeable after eating large meals. To serve all the masters equally requires the patience and readiness of, obviously, a machine. That's where the Roomba enters this scenario -- always ready and ever patient.
I propose that the Roomba be fitted with a roll-under fetcher and a centrally mounted active bumper mechanism sufficient in power to eject a tennis ball. The quick responding robot thereby outfitted would be programmed to park itself just out of reach under the obvious piece of furniture and remain there on standby. Any stray ball actives the bumper and the ball is ejected back up its path, and if designed correctly, straight back into charging dog's range.
I personally think this would be oodles of fun, and think further expressions of this basic design will evolve.-- reensure, Dec 25 2004 Active bumpers http://marvin3m.com/em/index2.htm#popsPop bumpers -- repair and design. [reensure, Dec 25 2004] iRobot http://www.irobot.com/home.cfmMakers and marketers of robotic products. [reensure, Dec 25 2004] Another Roomba/Dog combination DeerAibo [theircompetitor, Dec 25 2004] Very fetching.-- 2 fries shy of a happy meal, Dec 25 2004 Could also work for kitties and their catnip mice.-- TeaTotal, Dec 25 2004 I likes it. Not sure it'd fit under the furniture, but I likes it.-- half, Dec 27 2004 This needs to record/play MP3s to further captive your pet.-- reensure, Dec 31 2004 random, halfbakery