On the N810 it was possible to connect an SPP keyboard using a package called kbdd written/maintained by Frantisek Dufka <dufkaf@seznam.cz>. I have not (yet) tried to use that package on the N900 so I don't know if it will work or how much modification it would need. I will eventually because I have an Elektex cloth keyboard that uses SPP that I used to use on my N810 (I added support to kbdd for the Elektex keyboard) that I will someday try to get to work with the N900.