I stumbled on an interesting #OpenStreetMap changeset, and found the edit was made edited using #FireYak

Found it in the app store, saw an empty github repo, a blank website, and some mentions in the osm wiki, but not much else.

The screenshots from the app store seems to suggest it's only using OpenStreetMap tags.

Have you tried it for editing fire hydrants?

P.S.
On a related note, there's also #HailHydrant in #MapComplete:

https://mapcomplete.osm.be/hailhydrant