@einebiene you don't need a smartphone .)
One simple thing to do is just house numbering, taking notes on a paper.

Or noting where there are empty areas on the map, looking at satellite imagery (available via the !osm editors both on web and desktop) and noting where something is odd (maybe missing a playground) then walking there and taking paper notes.

Actually, the only thing a smartphone is good for is easily upöloading gpx tracks, but if you already know where you are and have satellite imagery pen and paper tends to be a much faster tool (and then mapping on a desktop)

Just remember that connecting your account to your ohysical home is easy if you're mapping close to home, so either don't care, don't map near your home or use another alias.