Parrot's AR.Drone isn't short on intelligence - as we discovered in our recent review - but it's also the ideal platform for quadricopter-based experiements. Tinkerer Psykokwak has figured out Urbi integration - an open-source robotics software platform - to give the AR.Drone object-tracking abilities (in this case it can identify and follow a red ball) as well as broader control options, including a Wiimote, a joystick or pretty much anything else that can hook up to your computer, in a mere 25 lines of code.
Video demo after the cut
That last point might put something of a dampener on your impromptu AR.Drone object tracking fun, since the quadricopter needs to be hooked up to a computer running Windows, OS X or Linux to run the full Urbi software. However, that also means you can use the Gostai Lab software to come up with custom interfaces for the 'copter, handy if you're less than enamoured with the relatively basic UI of the official iOS app.
Alternatively, Psykokowak has a second - more risky - method that allows you to load a version of Urbi directly into the AR.Drone's own memory, running the software on the quadricopter's own processor. The risk is that you might wipe Parrot's original programming, and while the company is open minded in encouraging mods to the AR.Drone, that probably falls outside their warranty.