They are sold in a kit from Edmund Scientific and can do tons of things. Apparently, once you assemble it, it already works in three very basic modes.
Those modes are obstacle avoidance, sound control, and following a line. Using a Windows-based PC you can connect the bot via a serial cable and use the included software to do so much more.
There are 180 possible instructions using the software. This would be great for someone in your family who is into robots, electronics, or just plain fun. They are available now and are even on sale right now, down from $99 to $77. I reckon that if you were real nifty you could add other features and functions to the laptop just by attaching something to it, like a drink holder or a dog leash, depending on how big your dog is.
PicoBotz- Build-it-yourself programmable robot [via makezine]