When I look for inspiration for new projects or new ideas, I often look out for posts like yours. Things that people would love to have, which don't exist yet and solve a real problem. This is a really great idea... maybe when I have some time to spare somewhere in the near future, I will try to implement something like that :-).

Does anyone older than 14 really care about that?

Never underestimate the effect a few tweaks to the ancient parts of your brain can have. As one anecdote, I was quite surprised how much of a difference was made in my motivation by coloring my passing/failing test cases green/red using ANSI escape sequences.

It sets goals very clearly outside of 'I need a working system'.

Zynga made vast majority of its money from the people significantly older than 14. And they swear by gamification.