Latitude makes it easy for you to know where your friends are on a map. Instead of GPRS it uses mobile tower to track where the phone (and its user is)
As fast company says:
Users have to manually turn on Latitude before it will broadcast their location, so no one will wake up one day with their location marked unless they mean to. Also, Google's servers don't track movements--they merely provide the last waypoint where a user was marked. This means that you can't track anyone's daily pattern of movement, making Latitude nearly useless for prospective assassins. (Breath easy, Barack.) You can also determine the specificity of your beacon, showing an exact city block or just the city itself. Only friends on your contact list can see your location.
Your list of Latitude friends works much like your Gchat friend list. You have to request to be allowed to chat with someone, and they must accept you before you can talk to them. On Latitude, there's a little more middle ground, for the sake of social grace; you can accept someone else's location and share back, accept their location and hide yours, deny their location or block them. You can also change privacy levels for each individual friend after you accept them by going to their Latitude profile, or for all friends by entering the "privacy" menu in your account. Once you're up and running, you can display your location along with a Twitter-like message: "Getting lunch, come join me!" or "At the dentist, come join me!" Or something like that.
Of course, it promises to be a great utility for small and medium enterprises who have a handful of employees - to keep track where each of them are - and understand which area would be better for meeting.
I turned on Latitude on my Nokia N63, and it works like a dream. Of course, the best part is that you don't need a jazzy mobile phone. You can also update that on a PC too, merely by going to http://m.google.com/latitude and entering your google account id, and then invite all your GTalk friends to join you.
Oh yeah, and if prospective clients also accept your invitation, you can just hop across and meet them.
As a blogger I also wonder if it has any integration planned with Google FriendConnect in any way. Imagine the possibilities then. We could have geographically aware communities around blogs/sites too.
Hmm, intriguing as well as scary in some way. Thank goodness it's opt-in.