The visitor counter app is tally counter that allows you to count visitors in and out of your theatre, club, venue, event, office, shop or store.
Multiple personnel, managing different doors, can run the app on their device, counting visitors in and out.
Each door attendant can immediately see how many people have entered and departed through their door along with the current total occupancy of the building.

Each app talks to other copies of the app via WiFi over the local network (technically the devices need to be on the same IP subnet).