For anyone looking to use gpsd in conjunction with something else or otherwise use multiple apps with one GPS receiver,
XPort (currently XPort3, previously XPort2) works pretty well. It has a
support forum with a friendly author. Admittedly it seemed to take a while to recognize my hotplugged USB GPS receiver (PL2303-based) but after it saw the port it did allow me to run Kismet and NetStumbler simultaneously yesterday (analysis later; NetStumbler got some that Kismet missed) with full GPS support.
Pointed to by
rage, hadn't seen it mentioned elsewhere here yet. Please add to guide if it works for you.