maybe you have to pair the devices first

moby:~# hcitool scan
Scanning ...
        00:15:7F:00:51:08       Bluetooth GPS

moby:~# hcitool cc      00:15:7F:00:51:08
moby:~# hcitool con
Connections:
        < ACL 00:15:7F:00:51:08 handle 41 state 1 lm MASTER 

moby:~# rfcomm bind /dev/rfcomm0 00:15:7F:00:51:08

moby:~# cat /dev/rfcomm0 count=10

moby:~# killall -9 gpsd

moby:~# gpsd -p /dev/rfcomm0