While iOS and Android rule, and Windows Phone dukes it out with BlackBerry for third, a new player will enter the smartphone fray in Q3 this year.Ubuntu powered phones will be on store shelves in October, according to Canonical CEO Mark Shuttleworth in an interview with the Wall Street Journal. He also says that app developers will get access to the latest build by the end of February, so long as they have a Samsung Galaxy Nexus to install it to. Developers are being lured by the promise that native apps written for Ubuntu phones will also work on desktop computers, and vice versa. Hopefully this fills the Ubuntu app store for richer offerings than we tend to find on mobile app marketplaces.Mobile computersThis interoperability between mobile and desktop computing is key to Ubuntu as a successful smartphone OS.