Javier Henderson writes:

Bluetooth may affect GPS receivers since GPS signals 1.2276 Gigahertz
for the L2 frequency...

I have used my iBook with a D*Link Bluetooth dongle and my Nokia 3600
phone in my plane, while flying, without ill effects to the Garmin
GNS430.

This is but one data point, anecdotal, and not rigorously tested.

I have a Bluetooth GPS receiver. It seems to work without interfering
with itself.

--kyler