gpsd is a service daemon that monitors one or more GPSes 
attached to a host computer through serial or USB ports, 
making all data on the location/course/velocity of the 
sensors available to be queried on TCP port 2947 of the 
host computer. With gpsd, multiple GPS client applications 
(such as navigational and wardriving software) can share 
access to GPSes without contention or loss of data. Also, 
gpsd responds to queries with a format that is substantially 
easier to parse than the NMEA 0183 emitted by most GPSes.

WWW: http://gpsd.berlios.de/