Configuring a Bluetooth GPS receiver on Gentoo was pretty straight forward for me.
This assumes that you already have the bluetooth stack up and running on your Gentoo box.

# emerge -p gpsd

# hcitool scan
Scanning …
00:0B:0D:6E:65:8A iBT-GPS
# sdptool browse 00:0B:0D:6E:65:8A
Browsing 00:0B:0D:6E:65:8A …
Service Name: SPP slave
Service Description: Bluetooth SPP V1.23
Service RecHandle: 0x10000
Service Class ID List:
“Serial Port” (0x1101)
Protocol Descriptor List:
“L2CAP” (0x0100)
“RFCOMM” (0x0003)
Channel: 1
Language Base Attr List:
code_ISO639: 0x656e
encoding: 0x6a
base_offset: 0x100

# rfcomm connect 0 00:0B:0D:6E:65:8A
Connected /dev/rfcomm0 to 00:0B:0D:6E:65:8A on channel 1
Press CTRL-C for hangup

On another terminal, start the gps daemon.

# gpsd /dev/rfcomm0

The fun begins:

# xgps