There is a tendency to see Google's Android and Apple's iOS as the only two smartphone operating systems that matter. After all, nobody would suggest that Microsoft Windows' position on PCs could now be supplanted by Apple or Linux.

On smartphones, however, there are still a number of other operating systems which have varying chances of success at taking market share. These include established players like RIM's Blackberry, upcoming challengers like Microsoft's Windows Phone, and then a number of smaller OS projects such...