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Google will tweak the mobile version of Google Maps to allow developers to layer information over the application, a feature that it hopes will lead to new uses.

The search company released on Thursday a subset of its keyhole markup language (KML), which developers can use to create place markers to highlight points of interest on the version of Google Maps accessible by mobile phones and handheld devices.

Gummi Hafsteinsson, product manager at Google, sees a wide variety of uses for the technology for mobile users. For instance, a hotel could create a KML overlay that flags the location of restaurants and stores providing special offers on food or goods. Another application could be a KML overlay that provided real-time information on gas station prices, he said.

Annotate Google Maps

Google hasn't made any assumptions on exactly how people might use the new mobile capability, according to Hafsteinsson. "We want them to try it out," he said. "We're going to lay low and listen to their feedback before we decide on future directions."

KML was originally developed for Google Earth, the company's online view of the globe consisting of navigable digital satellite images, to manage three-dimensional data. Google acquired the technology behind Google Earth and KML when it bought digital mapping company Keyhole in October 2004.

Developers can use the full-blown capabilities of KML to add a variety of different annotations to Google Earth's images of the countries of the world, including the ability to render three-dimensional buildings. Users can also add data to the Web-based version of Google Maps via KML.

Given the limited rendering capabilities of today's mobile devices, the KML overlays developers can create for the mobile version of Google Maps mostly concentrate on place markers, Hafsteinsson said. While developers can access the KML overlays they've created for the online versions of Google Earth and Google Maps from their mobile devices, more complex overlays involving sophisticated rendering may not fully display on phones and handhelds, he noted.

Last month, Google added two features to the mobile version of Google Maps--real-time traffic information for around 30 U.S. cities, and the ability to save routes that users take on a regular basis. The popular routes feature is available in all the countries where Google Maps for Mobile is offered--Canada, France, Germany, Italy, Spain, and the United States.

Google Maps for mobile devices is free and works on over 100 Java-enabled mobile devices, including phones from Cingular and Sprint, as well as Research In Motion's BlackBerry color devices. As yet, the mapping application doesn't support Palm devices; Nextel or T-Mobile USA phones; or phones from Verizon, Alltel, and U.S. Cellular that use the binary runtime environment for wireless (BREW) application development platform.