Service daemon for mediating access to a GPS
http://developer.berlios.de/projects/gpsd/

gpsd is a service daemon that mediates access to a GPS sensor
connected to the host computer by serial or USB interface, making its
data on the location/course/velocity of the sensor 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 a GPS without contention or loss of data.  Also,
gpsd responds to queries with a format that is substantially easier to
parse than NMEA 0183.