Yeah good point.... what will the good people of Nostr tag? For me it's mostly cafes and food but as long as you're in the current place I allowed anyone to tag anything. I wanted to do that to restrict somewhat what people could tag but that may change. I call it 'proof of walk'😉
But also it would be possible to tag a shop which accepts BTC  or even grab this info from various API like that which BTC Map uses. This app would allow reviews in top so an added bonus as well as the chance to earn zaps for your contribution...