[capableweb]

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.

[stereo]

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!!

[habi]

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