Facebook holds a press event today and they’re expected to unveil a geolocation service. Most likely it will involve the ability to identify where you are when you update your status, so it’s not just what you’re doing but where specifically you’re doing it.

Geolocation is the idea of using your smart phone to report where you are as you go through your day. A company called Foursquare is the leader of this movement. They’re best known for letting you become the honorary “mayor” of a restaurant or cafe if you check in there enough. It’s fun. But big tech companies like Facebook are taking it very seriously and investing heavily in the idea of geolocation.

Indeed, geolocation is supposed to be the next big thing online, the tool you won’t be able to live without. But how might you actually use it?

We talk to Tasso Roumeliotis, CEO of Location Labs. It’s a company that provides geolocation data to companies that build applications. He says geolocation as it stands today can be used for three big things: socializing, safety like knowing where your kids are, and shopping.

We also talk to Baratunde Thurston, a comedian and web editor for The Onion. He’s made a sort of art project out of running for Foursquare mayor of the New York restaurant Delicatessen. Even held a rally.

He’s having fun but thinks geolocation could grow into something more valuable.