The Xbox 360 lords a (rapidly closing) lead over the Wii and PS3, but the fact it arrived much sooner than those is starting to show. One particular feature that both the newer consoles have is motion-sensing controllers, allowing gamers to use their arms to play a game rather than just their hands. This has been exceptionally popular on the Wii, which has made motion-controlled game a huge part of their selling point.

Now, a third party has sought to incorporate the same sort of feature into the 360. "Talismoon"'s mod(along with a scarce few other groups), which requires physically modifying an existing controller, adds a few new forms of control on top of just plain motion sense:

The modification adds two buttons on the back of the controller, which are used to control various functions. For example, the tilt maybe enabled or disabled, along with adjusting the sensitivity, angle and inverted settings.
While the mod is very interesting, it is just a novelty at this point. Obviously no games have been designed to support such a feature, making wide appeal impossible. However, the very fact that some have gone so far to create such a mod begs a question: Given Microsoft's claim of the 360's "evolvability", will they upgrade their controllers to match features of their competitors? They have already proven themselves willing to attach new components such as larger hard drives and HD DVD drives. With as modular as the system is, I think there's a high chance that with increased competition from the Wii and PS3, Microsoft will seek to slap new functionality on their console as well.