The T-Mobile G1 is getting better and better. By the launch time, T_Mobile G1 needed more improvements like a touch screen keyboard, auto rotation and now a multi-touch feature. Seams like now, not only the iPhone will have this, but also the T-Mobile G1.
Still, the G1 is capable of tracking two touches at least, although three would almost certainly be impossible to manage, the system would be limited to simple gestures like a swipe. Fortunately, double touches work fine for most of what they are needed for: zooming and (with a little hackery) rotation.
More information here