Well to me a way around this could be to leave user bread crumbs. For example if its not an extremely populated area when a user leaves the area, a message coul

Well to me a way around this could be to leave user bread crumbs. For example if its not an extremely populated area when a user leaves the area, a message could say user "johns" was here 10 mins ago. contact him with a PM or something. That way you know that users are in the area using the app and may come back.