BY SIMON COHEN
Sitting — whether in front of a computer or a TV or, sadly, even while reading — is shaping up to be the single biggest avoidable health risk we face. Which is why there’s been a tsunami of tech products and a growing collection of apps designed to get you off your butt and into high gear. The latest in motivation? Apps that reward your increasing levels of physical activity with something everyone wants: cold hard cash (or at least its equivalent).