Sentry robots like WowWee's Rovio are all well and good - wandering around your house while you're away, and allowing you to log-in remotely and make sure nothing amiss is taking place - but they generally fall short when it comes to actually dealing with a problem. That was the starting point for RoboCommunity member Colt45, who hacked his Rovio into a remote fire extinguisher.
The modifications are in two parts: firstly, the hardware upgrade, with Rovio getting its own CF2ClBr (aka Halon 1211) flame-retardant fire extinguisher complete with a remote-controlled nozzle. Sprayed onto a fire, CF2ClBr starves the blaze of oxygen and thus extinguishes it.
Second comes the software side: on its own, Rovio can't differentiate between normal, not-on-fire objects and flames. Using a machine vision app and the Rovio API, loaded on the home computer, the robot can now identify fire and automatically spray it with the extinguisher. It's likely to only be effective on smaller fires, but coupled with a pre-programmed sentry route, it might be enough to oust flames before anything too serious occurs.