Saw Myles Borins give a talk about Empathy on JSConf Iceland last week, one of the best talks of the conference and some really good points there.
The talk is not available online (yet!) but I know it will be soon at https://2016.jsconf.is/ but I found this talk by him which seems to be based around the same concept: https://www.youtube.com/watch?v=GKTSvI8qw_M
A site showing stats from the English Premier League that you do not see on the usual football sites. You can for example easily see how a team is doing compared to the same fixtures last season (http://plstats.com/#/ComparedToLastSeason/Liverpool).
It's cool because this is my first try at a passive income (ads) and its mostly built using tools/frameworks I have never used before: Go, MongoDB, AngularJS, Bootstrap, Amazon EC2.
Can't recommend it highly enough.