This is an interesting little application, if you have a compatible phone you can install Google Maps onto your phone and latitude will display your location to your friends on a map. Likewise, you’ll be able to see the whereabouts of your friends. Perhaps you could use it so your significant other 
can keep tabs on you so you get a nice cup of tea and a meal when you get back from a ride! It’s got to be better than continually calling to say how long you might be!
http://www.google.com/latitude/intro.html
Privacy issues are largely overcome by the configuration options available to you, you can even tell latitude you’re somewhere you’re not if that makes you happy! You don’t actually need GPS in your handset, latitude will attempt to locate you using GSM triangulation, but GPS adds more accuracy.
Tags: Google Latitude