Would be wonderful if something similar exists for iPhone. There seems to be a few apps that are trying to make something in that direction but aren't as polished/nice to use as Street Complete.

Have you tried Every Door? It's a similar micro-editor for iOS:

https://wiki.openstreetmap.org/wiki/Every_Door

For more complete editing, I like to use "Go Map!!"

https://wiki.openstreetmap.org/wiki/Go_Map!!

Go Map!! recently introduced “Quests”, which are a bit like StreetComplete.

StreetComplete is fun! I was riding the bus the other day, and I opened the StreetComplete app. I noticed that most of the bus stops had incomplete information, so as we rode by I answered questions like "does this bus top have a shelter" for each stop as we went by. It's very easy to use, and I get a feeling of making the world a tiny bit better.

This is awesome, thanks! I just got started mapping my neighborhood. I'm gonna have a lot of fun during downtime at work.