Wouldn't Google Now at some point do all of this ? I think I guess Shifu makes it a little more mutually controlled.
It would be good if this learns over time on what to remind and what not. A pebble app integration would be nice.
Having used it for sometime now this is the smartest one. I keep guessing at their algorithm on finding my free time because it gets pretty close. Good application.
Anyway, nice to see a unique point of view at an age old problem!