I too would like to get functionality with my Earthmate, I did locate a link where you can download a custom software patch to convert the Earthmate's output to NMEA, although it does its work in a software buffer for use by GPSS software specifically, as I recall. If it helps, email me an I will dig up the link.
At any rate, if the Netstumbler software gods could find it in their interest to interface the GPS' input from that software's output buffer file, maybe there is a match here.

Thoughts?