"Really, a $500 clapper?"
Wow! Talk about missing the point!
Thanks to the OP from bringing it up...we've been using it for a couple weeks with the 5d2 and 7d for syncing second system (and third system

in some cases) sound in our production.
The iPad does a few more things than "Clap!" We use it for our dailies, still sharing, resource for web stuff...as well as several entertainment apps. Script writing, notes, contacts for contractors, scheduling, and we've even put a Korg synthesizer on it for some SFX. We've also had some fun with field edits of some photography for use on the story board.
Much more than a "Clapper"...and at $500 (which is a bit low, most models are a hundred or three more

)...they're a bargain on set, IMHO. Of course, as always, YMMV.
It's a killer app...and I wouldn't put Jam-syncing time code out of the realm of possibility of development. With the camera connection kit, hopefully a developer much smarter than myself will come up with a cool way to sync from field recorders, cameras, or all of them down the USB pipe, OR, BlueTooth would be cool if there was some sort of Time code base station for all the components in the chain. Here's to hopin! I've found the iPhone, and in the last couple of months...and to a MUCH greater extent, the iPad invaluable on set. As someone else mentioned, they are fragile...so a decent case and sure hands are essential. I use my MBP much less these days, and the form factor allowing for things like a workable slate for sync work in post is invaluable.
J