I occasionally recommend Beeminder¹ to other students at my University² and today for the first time the response wasn’t “cool, I’ll have a look” but “funny that you bring this up, two people told me about it already”.
I can only assume that those two recommendations are the echo of my prior preaching 
¹ and sometimes bribe them with stickers
² in southern Germany, so not exactly home turf for Beeminder