I know I can tether to a laptop via PDANet but will it work with an iPod Touch or iPad via bluetooth?
Not without jailbreaking.
The bluetooth drivers on the iPod and iPad don't fully implement bluetooth. I haven't heard if 4.2 will change this. I doubt it, but I also intend to run a few checks to see what can be done.
In general on a stock iOS device you can use a keyboard, bluetooth audio, and transfer files between your computer and iOS device, though I can't always get this to work in both directions. There are probably a few other things, but I can't think of them at the moment.
Last edited by TwerpPoet; 11-06-2010 at 08:55 PM. Reason: removed erroneous info about SD card access