The bluetooth stack (Bluez) in the linux kernel allows the use of the bluetooth serial port profile. This is also known as an rfcomm channel. Unless nokia messes with the bluetooth stack of the linux kernel (unlikely), communication with the metawatch should work.

BTW, Thanks for the notice on the fossil metawatch, I hadn't heard about it yet. I've played with the sony ericsson mbw-150 watch in the past with my nokias (mbw-150 to N900 works over rfcomm). I may need to pick up the metawatch and start development with the N900.