Google has launched a music store and streaming service to rival Apple's iTunes, allowing customers to buy tracks directly from the Android Market.

Google Music lists more than 13 million tracks from labels such as Universal, Sony and EMI, and allows the saving of playlists online and the sharing of tracks with contacts through Google+.

The service also offers exclusive tracks from the Rolling Stones, Pearl Jam and Dave Matthews Band. Google has promised to court independent artists and smaller labels through the Artist Hub site.

"Google Music helps you spend more time listening to your collection and less time managing it," said a blog post by Andy Rubin, senior vice president of mobile at Google.

"We automatically sync your entire music library, purchases and uploads, across all your devices so you don't have to worry about cables, file transfers or running out of storage space."

Google Music could present the biggest challenge yet to iTunes. Apple has defeated all challengers to date, but Google has a huge brand and the resources to go head to head with the market leader.

It could also wean some people away from the Apple brand and convince them to move to Android.

Google Music is currently available in the US, and will be expanded to other territories soon.

Those who were hoping that the fuss over the iPhone location logging report would be short lived got some bad news on Monday.

First, there was word that Apple's head honcho is officially speaking out on the matter. In response to an email inquiry from an iPhone owner, Steve Jobs not only denied that the company tracks its users, but accused Google of tracking users with the Android platform.

"Oh yes they do," Jobs said of Google. "We don't track anyone. The info circulating around is false."

Perhaps Jobs was just saying that Google records the same location data that Apple does, and that neither company actually tracks users. Or perhaps he was accusing Google of using data in a way that Apple does not. It's a safe bet that Jobs left the message vague on purpose so that people would wonder just that.

Either way, this is unlikely to be the last we have heard on the matter. US Senator Al Franken (yes, the former comedian) is seeking to call executives from Apple and Google in front of a government committee to testify on the matter of mobile phone security and privacy.

The hearing is scheduled for 10 May at 10am (1500 GMT) and should be mandatory viewing for those interested in mobile security, privacy and user rights.