If something like what I just thought of is out there then please let me know so I can use at at some point. If it does exist, I hadn't heard of it so here's what my idea is:
There are plenty of apps that help people measure their physical activity and plenty that give dining discounts, so why not combine the two? If someone is very hungry because they exercised extensively, wouldn't it be nice if they got a discount so that working up an appetite won't be an economic strain? This would only apply to large portions and carb loading the night (maybe 2 nights) before a big race. Would have to figure out some way to minimize fraud, but making this app would not only help drive business to restaurants but provide a public service by encouraging exercise.