It wouldn't be hard to build, finding the time and the motivation have been the stoppers for me for things like this as I personally don't care about Achievements. It took me over two years to getting around to tracking reputation! Having said that, I'm trying to spend more time with WoW / Jamba, but I tend to focus my efforts at patch time. I keep on thinking I should roll something like a kickstarter or an indiegogo to help motivate me, but I think Jamba's doing pretty well considering the scope of it and how long I have been supporting it.