Would it not be interesting to see if people around you are using a Google/Apple API based Corona Contract Tracing app? Calliope can help.
Social distancing tracker that helps you distance socially better using bluetooth
Realtek Ameba RTL8722DM built in BLE Beacon Service example from Arduino IDE.
Databat.io's Sonar is an open source tool that enables you to turn a Raspberry Pi into a sensor for people density.