Modifying carman to read a serial port directly makes the most sense, as that's all it's doing anyways, but wrapping that functionality in some bluetooth connection code which we don't need. The bluetooth-serial serial-usb would work, but it's a pretty kludgy approach and completely unnecessary as far as I'm concerned. If I've got some time this afternoon I'll try grabbing a copy of carman SVN and see if I can build a "simplified" connection function to route the current bluetooth commands to any serial port. If you don't see anything posted up about it in the next few days send me a PM to remind me please.

Thanks!