It's probably going to pay dust even for an intensive workout. I like the idea but to really motivate people, the reward has to be significant, i.e. you'd have to be able to buy at the very least an isotonic drink or a protein bar after an hour of running the app.
If insurance companies put it out it wouldn't pay dust. Take bluecross, they have a website to log things, report activity, etc, for points. With these points, you can easily get hundreds of dollars worth of stuff from their catalog. The problem here, is no one that you will be paying for insurance is going to be backing it. So instead it's the marketing dollars they can generate. I truly doubt at this time if you'll ever recoup the cost of the new monitoring device you will have to get.
It's an interesting idea, but I don't think it's going to work.
First, they accept very few devices, most people have maybe a heart rate monitor with no bluetooth connection.
Then, I only would see it as really motivational (personally) if I could also LOSE money - skipping workouts, not bringing it... that way you could increment the amounts offered.
Awesome, a couch potato penalty working against your balance.