It's specifically for lifehacking data nerds (so probably most people here on HN) and the idea is to combine a quantified self tool with a commitment contract. Specifically, you pledge (actual money) that you'll keep all your datapoints on a "yellow brick road" to your goal and if you don't, we charge you.
We integrate with various gadgets and apps like RescueTime and Trello and GitHub (also fitness things like Fitbit but I guess this thread is more about productivity-related motivation) so, for example, you can force yourself to waste less time on Facebook or commit to GitHub more often, or enforce a steady rate of moving Trello cards to the Done pile.
[repeated from a very similar Ask HN thread the other day: https://news.ycombinator.com/item?id=6121572 ]