Is the P5 glove useful for anything?

Unfortunately not. While it looks cool, and is affordable, that's where it ends.

The bend sensors work good enough, but the positional/orientation tracking is unacceptable. It barely works at all, gets lots of jitter, loses tracking constantly, etc. It just wasn't designed very well, even at the time it was new.

There are a bunch of different options coming soon, for now you will probably be OK with a Razer Hydra (if you can find one).

They are ok (better than any alternatives < $100 I think) if you combine one with a Hydra, aftermarket optical, or other tracker. As cyberreality says, the positional tracking is crap.

I wrote a Unity3D dll/demo for them, and also a Hydra integration mouse driver - they're on mtbs3d here along with some more detailed info about my findings after using a couple of P5 gloves.

http://www.mtbs3d.com/phpBB/viewtopic.php?f=145&t=19550