Just for fun (since Im a dork), I was looking for a wireless stumbler for Macintosh that supported a GPS unit because I thought it would be interesting to map how many wireless networks there are in my neighborhood (I usually can see 15-30 unique wireless networks from any given point). In my search, I ran across one called kismac that does exactly what I wanted (it even generates the maps for you, so I didnt need to code something to plot the GPS coordinates on a map).