I've been using HabitRPG for a couple of months and I don't have freakishly great self-motivation (although I do have a friend who's in my party, so there is some peer pressure/accountability to keep me on track). So far I've found that it's good for habit formation for the kinds of things that are more about remembering to do them than about negative motivation. It's also reasonably good in a GTD sort of way, in the sense that I'll put a big task on my to-do list, and then when it comes time to actually start on the task I break it up into much smaller subtasks to provide myself with incremental rewards towards completion.

If you don't know, I would like to point out that you can run a server locally without almost any effort (there are detailed instructions on the site), thus avoiding crashing problems and allowing you to access it offline.

I've tried using HabitRPG before, but didn't stick with it. I've started using Lift, working out every day following the http://7-min.com. Somehow the expectation of checking off habits for today keep me going through the motions, and the automated timer reduces friction of changing into the mental state appropriate for exercising.

High Intensity Interval Training (H.I.T.T.) may have the same benefits as running and is a more efficient use of time: http://well.blogs.nytimes.com/2013/05/09/the-scientific-7-minute-workout/

Read the linked journal article.

Don't do HITT with low available glucose (blood and liver); your body will eat through what's present quickly, won't have enough time to prepare more, and will break down skeletal muscles for energy instead. I doubt this should prove problematic, but omitting this caveat is simply irresponsible.