I'd say any innovation that can provide competitive play or rewarded play through phone apps (or even just a website with player profiles that connects directly to systems setup on pins) should be a top priority. Kids have their ticket reward systems (which are admittedly still fun as an adult), however, a more "adult" system that was geared toward competitive and single player "goal oriented" setups for teens and adults would be excellent.
I love playing the tournaments in the Pinball Arcade app - it's still competitive, but it's also much less intimidating than going to a real tournament. I think there's a great market for this with everyone who already likes pinball... But just as importantly, it would be a potentially exciting way to usher in new interest to pinball overall from the outside as well.
I think I've read a couple things on Pinside over the past year about people working on this already? If not, it really really really should be done.