Neat idea. I already do something similar through the Higi website, formerly Earndit. You get points for miles ridden (or walked/run), and can use them for discounts at online merchants OR donate the points towards a charity goal. I always do the latter. My favorite charity there Deep Springs International, which works to provide access to clean water for Haitians, but I’ll have to check this out, too. Higi’s nice in that I can just use my Garmin and sync up miles from pre-existing services like MapMyRide (no Strava support yet, though I think it’s in the works), but I’d be OK tracking my rides on my phone if there’s a worthwhile charity I could be helping.