It occurs to me that Beeminder’s IFTTT integration could be used to implement goal referees similar to what stickK offers. For example, you could create one IFTTT recipe that tweets every time you post a data point, and another recipe that derails your Beeminder goal (i.e., by posting a data point of a certain positive or negative value) if a Twitter user of your choosing replies to that tweet with a certain phrase or hashtag.
Before I fiddled with this any further, I thought I should ask the people here for their thoughts. Any ideas on how to implement this more elegantly? Any ideas on how this could be implemented with Facebook instead of Twitter?