We process technical Wi-Fi identifiers (MAC addresses) only momentarily at the sensor level. Device-level data is used solely to calculate an aggregated audience count and is irreversibly deleted immediately afterward — our solution does not retain persistent device identifiers and does not track individual smartphones across visits, locations, or campaigns. Only anonymous, aggregated statistics are transmitted to and stored in the cloud. This processing is based on legitimate interest under Article 6(1)(f) GDPR. We also encourage local information signs display for the audience to be aware of the count being performed.