I believe somewhere I read a bit about this link you sent. I'm actually starting to think it's a great idea for commercials and interviews. Anything where it's not a pain to tie down the camera. Also the FRC ability of the unit is nice to have on set. Load it right into the computer. The client walks away with the tape as well.
I would have to agree that a camera mounted P2 unit would be handy, but it might be somewhat limited in it's functions.
I too would like a portable P2 recorder that is small and easy to mount on the camera. But, connections are still the biggest issue. The firewire jack bites. That's what's keeping me from buying a Firestore. Now, if they could make it work off HD-SDI with BNC jacks, that's much more dependable.