The issue is that the 20 apps people use are different. People want to have a banking app on their phone that they can use to deposit their checks. Basically, a bank of any size will have an iPhone and and Android version of their app. They don't have the resources to do a third platform.

There are various toys that use an app on the phone for control. They are also iPhone and Android.

I tried Windows Phone. I really liked the platform. But the lack of apps for such things like my bank, etc made me leave the platform. If Microsoft with all its resources and developer outreach was unable to get a critical number of apps for its platform, I don't see much hope in another mobile platform succeeding.