For mobile apps, the biggest challenge after getting developers is finding revenue streams. Sure some game developers can offer in-game upgrades, but in general things are not as rosy as they seem. Where Inc., a Boston-based company that started out as a geo-location centric app, is trying to chart an interesting course for itself — by becoming a location-based ad network, which launched in March 2010. It is doing about a billion impressions a month and reaches 50 million consumers.

Today, the company announced that it has bought Newburyport, Mass.-based LocalGinger, a local group-buying service targeting second-tier cites SUCH AS….. The terms of the deal were not announced. Where is betting that with its advertising platform and LocalGinger, the company can create offers and drive real-time, hyper-local commerce.

Where isn’t the only location-based services company that is trying to break into the local advertising market using new methods. I recently wrote about Pelago, which along with the likes of Foursquare is going after location-based marketing campaigns, which ABI Research estimates will be a $1.8 billion opportunity in 2015.

Related content from GigaOM Pro (sub req’d):

* Research Report: Location — The Epicenter of Mobile Innovation
* Is Geolocation a Real Business or Just a Feature?
* Shopping Matters When it Comes to Location-Based Apps