Wife and I occasionally institute one of these workout challenges to motivate physical fitness and general healthy living. I recently peaked at my all time high weight and i'd love to shed a couple lbs, tone it up a little and give the ole ticker a tune-up.
From now until New Years you must workout 4 times a week. You may workout twice in a day. Workouts are defined minimally, really any 20 minute activity where you might break a sweat (or 4 miles of extraneous walking). After New Years it's 5 times a week with only one double permitted per week and no more than 2 consecutive days w/o working out. Each week you fail to perform you lose money off your discretionary budget for the month and the person who fails the least at the end of the challenge (Feb or Mar, not sure yet) gets to plan our next vacation - carte blanch no holds (read: $$) barred.