I usually carry a few stickers on me just in case, so people can remember OSM and look it up later (after I explain what I'm doing and say it's a fun community project).

> it's not like they can call the police or anything

Well, they can. Whether or not the police will bother doing anything can depend on a lot of factors.

Yeah, I love OSMAnd for that reason. With it, you can add POIs and for more complicated edits that need a bigger screen etc. it's easy to add OSM Notes (which other mappers can then follow up on). Notes I find particularly good when I'm travelling and don't have time or enough knowledge of the area to actually edit the map, but want to help others do so.

Go Map! is indeed a fine app. But it does require some OSM knowledge, like the various tags. In that regard the linked Android app is a lot simpler.