Theres several low power GPS receivers out there (ex. Trimble's Lassen iQ), but aside from the hardwre interfacing to it what else is required?
Ive never used or owned anything with GPS, just figured it would be a neat project, but is gps data free, just hook up an antenna and go? Or does it require some kind of existing account for authentication?
You probably want a unit that outputs NMEA 0183 "sentences" (formatted ASCII text). Google for "GPS NMEA 0183" for loads of info. Fairly simple to interface with.
The antenna, front end, and signal processing are often all in a single package for consumer units, although systems with separate antennas are available.
If you're shopping around, also look for systems that support DGPS and WAAS as well as, perhaps, a dual frequency system that can take advantage of the L2C signal as it is implemented.
Just getting a lat/lon position may become boring pretty quickly unless you have a set of charts/sectionals to plot positions on. If you need maps to go with it, the DeLorme "Street Atlas USA" product will interface with NMEA 0183 units as well as their own USB-powered GPS gadget. They have a topo product as well and there are other, similar products.
I just ordered a Polstar GPS mouse which looks interesting. Slightly bigger size than a usual external GPS antenna and it supplies direct TTL as well as RS232 serial I/O. An add-on cable came with it to connect it to a USB port (no external power needed). Price about 70 Euro (90 USD) incl shipping.
Is anybody familiar with a Polstar GPS mouse? The manual claims power consumption is only 120mW in "tracking mode". Power can be 5-9V DC, which would mean only 24mA at 5V. That seems hard to believe.