Google is working on a search service exclusively geared to finding mobile downloads such as ringtones, reports The Wall Street Journal.

The new service will be a subset of the larger mobile-friendly search site it operates. People seeking ringtones, wallpapers, games or other content can search for just that. The immediate ability to buy what is found would likely then be facilitated straight from the search results.

Such a move promises to be an immediate threat to mobile carriers that have tried to keep customers on their own storefronts for such features. The cooperation of those carriers will likely depend greatly on whether the functionality goes through, or around, their own e-commerce sites.

While it's reported that Google has been working with content providers on the best way to index their offerings, there's no solid date on when such a service may launch. A mobile-content specific vertical search engine would be yet another opportunity Google could open for selling sponsored or otherwise paid links.