They are collecting the MAC address of the WIFI / Bluetooth in your mobile/Tablet.
Good example of Internet of Things, I am wondering if they are using Kafka / Cassandra to process all this data in realtime.
Possibly a dumb question, but how are they grabbing Bluetooth MAC addresses? My understanding was that you only broadcasted you MAC address in discoverable mode, and that after pairing, MAC addresses are entirely forgone in favor of master-slave addressing and frequency hopping synchronization.