Geomena is an open geo database of WiFi access points meant to be used for geolocation. The concept is similar to Skyhook (see our Skyhook API profile) and Google's Gears (our Google Gears Geolocation API profile). The difference is that the database is as open as Wikipedia, editable and downloadable by anyone to use however they want. Geomena officially launched an API for developers at this month's Where 2.0 conference in San Jose (video embedded below, with myself making the announcement).
Even with mobile devices with GPS becoming pervasive, WiFi geolocation will continue to be important, as Webmonkey describes:
You may be wondering what the need is for wi-fi location sensing when so many smartphones and laptops have GPS built in. But consider how unreliable GPS becomes once you move indoors — it isn’t always an option in an office building, inside an apartment, or in highly congested urban areas. Also, for the near future at least, there will be a class of mobile and tablet devices that don’t have GPS. They will continue to rely solely on wi-fi for location sensing. The cheapest iPad (which will probably be the biggest seller) falls into this category.
Geomena has let users add or edit access points one at a time since last September, when the project was created by Don Park. The API provides a way to be able to add data programmatically. It will enable applications that sniff WiFi and combine with location, either grabbed via GPS, address, or other methods (more details at our Geomena API profile). Some of the more exciting possibilities are games where WiFi is incorporated into play. Treasure World on DS does this, but has no way to report the data. However, Geomena has a long way to go. There are fewer than 5,000 points recorded right now. Most successful APIs combine a platform with a popular service, letting each build off of the other. If the data is there, developers will no doubt want access to it. But, it's unclear whether developers will also want to take part in collecting the data.