Any GPS receiver should work. I plan to connect it to my Etrex Vista. Regardless of the GPS device, you will need to buy a serial to USB adaptor to allow connection of the device to your laptop. Another interesting app to look at is MacGPS Pro. It is a program that allows you to download any map, quickly calibrate the image then run your GPS onto it. This allows you to follow your location on any map ie/ topographic maps. Very nice for camping, offroading hiking etc. Shoot me an email if you need any more info. I used to run a pc laptop to real time GPS in my truck and am now just starting to figure out how to run a similar set up with my new PB.
Jason