PSP World has details of Sonys latest Patent application, this time for a keyboard add-on and a cell phone attachment for the PSP.

Filing Patents is a waty of Sony protecting its position in the market with respect to these two add-ons, effectively ensuring that any third party manufacturer who wanted to provide either extension to the PSP functionality would need to go through official Sony channels and have their blessing. Any manufacturer releasing a keyboard or phone accessory would be in danger of breaching a patent and could be taken to court by Sony.

The Patent filing also implies that Sony are intending to bring to market the products themselves, although they could just be positioning themselves in case a third party attempts to market (and therefore benefit) from a PSP accessory.