Tinkerisk:
Governmental Corona Warning App (by SAP and Telekom)...
edit: It works decentral based on "keys" only stored on the devices for 14 days (no central servers). Bluetooth is used for distance and time (no location) dependent contact tracing (not tracking!).
14 days is a bit short, I think. And I don't think anyone has successfully used BT to estimate distance, so I guess it tells you if you were within 100m of someone.