Hi there, First thanks for responding to my question about the PDF download on the iPad you gave me the exact answer I was looking for and it was very helpful.
To answer your question, yes there are solutions for android to use pretty much any bluetooth device, i have seen everything from nintendo wii remotes, non-android phones, and keyboards (i have seen even apple bluetooth keyboards work) but no solution yet for any android based tablet. All require you to have a rooted device and there is not app based solution per say but the newest Cyanogen rom supports it fully and has been tested to work with a variety of devices. There have been proposed app based solutions that only require root and not switching roms but the it has been kind of sketchy as most of them don`t work with HTC sense based roms or device compatibility is extremely limited.
Unfortunately Cyanogen does not yet have a stable port any of the android based tablets as of yet. There is a official Cyanogen beta port for the Viewsonic G tablet and a final build is expected to me released soon. Nothing yet for the Xoom tablet and also keep in mind that the latest Cyanogenmod uses Android 2.3.3 and not Honeycomb 3.0 (yet).
For more info check out Cyanogen`s forums.