The mythical Google Phone has got the rumour mill running on overdrive this week, following speculation that the device might not be a device at all and is more likely to be a mobile operating system or an application platform.

Some believe that the GPhone project, as it has become known, is actually a full fledged operating system based on Linux, which will be given away to handset vendors without the accompanying licensing fees attributed to the Symbian and Microsoft Windows Mobile.

Others believe that Google’s mobile initiative will focus on a package of optimised for mobile services, that will either be preloaded on devices by the handset manufacturer or operator, or even installed by the end user.

But in both of these scenarios, advertising is expected to feature heavily. It is now believed that Google will embed advertising at every level of the mobile user experience and will not just associate it with the usual subjects such as mobile search and discovery.

Last year, Google chief executive Eric Schmidt caused a stir when he announced that mobile phones and services should be free. Schmidt believes calls could be paid for through advertising.

The industry is divided over whether an adverting supported model could work. Blyk, which recently launched in the UK, is being closely watched as the world’s first ad supported MVNO.