Put stickers on a calendar! (Use this for Seinfeld’s "Red X" motivation method. See support page.) Remember putting stickers on a calendar? We noticed that digital calendars are not so good for this, so we made an app for the iPhone. ShinyCal: Not to plan, but to reward!
In addition, we've used the GPS feature of the iPhone to let you "Location Lock" a calendar. When a calendar is "Location Locked" you can only add or change stickers if you are at that location. So the next time you are at your health club, you can "Location Lock" ShinyCal to motivate yourself to go there.
ShinyCal is free for everyone to enjoy. Coming soon: integration with the "Tweet Sheet" and other online services.