Isn't this essentially the model for wearables already? Except with the opposite relationship: the phone is the smart device and the watch is relatively "dumb". This makes sense since it is easier for my phone to be much larger and more powerful, I can also take it out of my pocket if it gets too hot, etc. It looks like in this case they've made the watch smart and the larger screen dumb, which is novel, but I'm not sure I see the advantages. Also, I am much more apt to lose my watch than my phone, but maybe that is just me.