I'm not sure what frequency it updates at. I just looked in the settings but it doesn't show how fast it updates. I'm guessing it's either 1s or 5s just from the way the tracking looks. I've been in truckstop lots and you could see the exact path I've driven through the lot on the satellite image.
Here's the link to GooPS:
http://goopstechnologies.com/
Also, ALK's CoPilot has built in live tracking and messaging. With their system the user tracking you can see your location and destination with ETA. They can also send you messages through the program itself. However, their Live feature doesn't seem to work too great. I've had unknown people send me messages and new destinations. I've also done the same thing to others by logging onto my own account.