Splayd
I used to think you could convert a lot of things [to an all-in-one smartphone] but I'm older and wiser, I think. You end up with a 'spork' - a combination of a spoon and a fork. It's no good as a spoon and no good as a fork.
They do actually exist (an example being the Splayd, and ironically they're actually quite good for the job.
As for the software, one has to wonder why there isn't any kind of industry-standard way to judge this. Or would that be too simple and straightforward rather than allowing all the trickery and marketing wordplay that now goes on?