The concept of a mass market device is sort of incompatible with the freedoms we generally associate with linux -- Android is really the closest thing we can hope for. It runs a linux kernel, a very non-standard userspace, and is relatively locked down (when compared to a general purpose linux distribution)

I think "linux smartphone" would end up looking very similar -- some UI on top of a kernel with a very non-LSB userspace; therefore the concept is really not all that compelling