Whereboutz is a new service powered by TeleNav that lets you announce your location for others to see, while mapping it to a geographical location. The service has two ways in the door, both as a Java app for phones that can run J2ME, as well as a Facebook application that accomplishes a similar feat without any sort of installation. Once linked up to your Facebook account, the mobile app will show you any of your friends' status updates on a map, as long as they're posting through Whereboutz (regular old status messages need not apply). You can also browse by who is nearby, and assuming you've got their number handy, you could attempt to meet up with them.
For users with less-capable phones, or who want to avoid data charges, there's an SMS version of the app. While you can't post your current location, you can get updates on your friends and what they're doing delivered as text messages.
I must admit I don't get this market of trying to keep tabs on people's geographical location at all times, but clearly there's some good use for parents keeping an eye on their kids, or for businesses who have delivery or response personnel spread out across a city. A big snag with Whereboutz is that it requires users to actively map out where they are instead of continuously doing it for them with something like GPS. It's also a tough sell to get users to adopt a second status message system, in lieu of finding a way modify Facebook's existing system to work with geo-data.
There are some other solutions that let you tell other people where you are including Loopt, which has a location alerts system that launched in November, along with Helio's GPS-powered Buddy Beacon service.