FireEagle, the service that Yahoo has developed for users to control their location-based information, and then offer it up to their favorite applications, will formally launch publicly this morning.

Expect to see details from Yahoo on its blog at 10am. It is being announced at the eTech conference in San Diego.

FireEagle significant because Yahoo expects it to be the most comprehensive location-based control system so far, and could make a breed of applications much more dynamic and useful. Yahoo has also opened it up for developers to use on any platform or application. The only caveat: Consumers will get to control what they want the system to have.

The project, which has been worked on for months at Yahoo’s Brickhouse in San Francisco, will offer APIs so that other applications can accept your location coordinates and feed it into FireEagle’s system too. Yahoo will first launch with several applications of its own.

Here’s how it works. You can set your phone, if it has GPS, to automatically update FireEagle with your whereabouts at regular intervals. You can also add information manually to supply precise information: You can text the system with your location, naming a cross-street in a city, a zip-code or even latitude/longitude coordinates.

Then, you can authorize an application like Flickr, for Facebook, to access your location information. Flickr can then stamp your location on the photos, which make them easier for you to file and organize, and for your friends to see where you are. All kinds of applications that can be used with FireEagle: It can be used with Twitter, so that users of the messaging system can more easily supply their location (and for example, they can choose to get messages from only people from New York; while some applications have been built to do this already, they haven’t been very accurate), and with local community sites such as OutsideIn and geo-blogging site Plazes (which has long let people report their location information). Some of these applications already collect geo information, but none of them share it. By letting everyone jump onto FireEagle, every has more information on more users.

Tom Coates, the Yahoo developer who led the project, and who I met with late last year, likens FireEagle to Paypal, a service in the “middle” handling the data. For example, even Google would be accepted, if it is willing to say, send information gathers from its own location technology using cell-phone tower coordinates. Loopt, another mobile-location service, is another potential partner (Yahoo’s argument is that it would be better able to monetize Loopt’s service, given Yahoo’s huge base of advertisers; there could be a revenue share). There’s also Skyhook, which gathers information from people with devices enabled with WiFi technology (image left). Whether these companies remain competitors to FireEagle or become allies is difficult to know.

Other applications might be enabled with this, Coates said: One might be to help you find a group of friends, by tapping into their cell-phone GPS location information, or a “Proximizer” application which gives you updates on where your boss is, or desktop photo applications tracking the location of your friends. It could be used in mashups with say, Last.fm, letting you hear what music your neighborhood friends are listening to.

The big question, of course, is whether users will play along. How much are you really going to be motivated to supply all this information willingly, and how often are you going to update it? It takes work. It’s not clear how much outside companies will contribute. But it’s a noble effort,