Ask HN: Which marketplace category misses an high quality app

I struggled to come up with a title that really sums up my question in one sentence, so here it is in more detail:

HN has both, people who use a lot of apps on a daily basis, and people who make a living with developing apps.

I thought we could collect everybodies opinion on what (kind of) apps have room for improvement. What apps are either completely missing, or you wish there would be a better alternative?

People who want to develop mobile apps, but don't have an idea for one, could pick a up-voted app suggestion and work on a more decent version of it. Win win for everybody.

This works for every platform, so I propose we format comments like this: [Platform, App Category/Or name of a specific app]