Logitech has released a teaser advert on its Facebook page that hints at a new accessory for the iPhone 5, iPhone 5C and iPhone 5S: a game controller.

Most likely a case-like device, whereby your phone sits inside with the controls around the outer rim, the Logitech controller is yet to be revealed for real. Instead, the company simply asks you to enter your email address on a "find out more" page to get the info when it becomes available.

How the controller will work is not yet known either. And the compatibility of games to work with it could be an issue. In the ad, the iOS version of Terraria is shown, but there are no details as to whether it currently features control support - such as with the iCade. If the same control codes as iCade are utilised, Logitech will suffer from the same issue - only a small number of the multitudes of games out there work with them.

The Logitech announcement is most likely in response to the unveiling of a rival product, the GameCase. The difference with the GameCase is that it also supports iPad. We currently don't know if that will be the case (no pun intended) with Logitech's.

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Pocket-lint will bring you more on this when official details are released.