edit: I was going to link a specific one I found a few weeks ago, but it turns out there are tons of them now, so I’ll just explain the idea. Most of these apps are basically reminder tools disguised as simple little games. A common example is a flower garden. Each “flower” represents a friend, and you keep the flower alive by staying in touch. That might mean sending a message or planning a hangout. If you don’t, the flower wilts, just like a real one would without care.