Once you jailbreak it, you have access to a full linux OS under the hood. We have a USBNetwork/sshd hack, as well as kterm (a KUAL extension) which is a terminal shell prompt.
Although the screen is not very big and it is somewhat awkward to type.
I don't see why you couldn't use a bluetooth keyboard though -- bluetooth support (on the new, supported devices) starts in the kernel, so you can just hook into that. You may need to set it up yourself.
I think in the past people have played with getting bluetooth up and running even on older devices before Amazon turned it on themselves...