I saw something at my local distributor the other week (am in the UK) that he told me did exactly this.
It was a global cache/command fusion/bitwise style system. Unfortunately I can't remember the name of it, but he was trying to wow me with the "you could just set it up with the clients favourite remote to do anything".
I asked how would i define selecting 4 different video sources from a matrix, to which he said it could be ANY button you want!

Nice idea, but the application will be a nightmare. Trying to explain to a client how to switch between, Satellite box, Apple TV, Blu-ray, radio & music would just be lost when you start saying this X button does Y, but then when your on Z it does F...