Clearly, if my years on the internet taught me anything, the killer app ID is an app that hack's ex's socials with bonus functionality for changing their school grades
I think you can use existing software to do that. If your store has wifi (even if you can't access it, I think), you can geofence an area and have some action (such as popping up a reminder app) trigger. I've not used software like this myself, but I remember people describing behavior like this at least on Android. If it might be useful to you, you should give it a search.
I have an app that's meant to schedule things, but I just use it as a checklist and preface each action with the location. So long as I check it (second home screen on my phone, so not a huge barrier), I'm usually good.
I had a guy recently ask why his printer wasn’t working after he got a new router, and it turns out it is because the printer only went up to 802.11g. I’m pretty amazed that printer outlived the wireless standard it was using.
The router he got did have support for 802.11g, but for some reason I don’t remember we couldn’t turn it on. It was some integrated 5G router. The solution was just to use the printer’s built in AP to print. He has to disconnect from the internet to print things, but it still works.