Future Wi-Fi devices will be able to see through your home and business walls, for activity monitoring and biometric identification, https://www.theregister.com/2021/03/31/wifi_devices_monitori...

> In three years or so, the Wi-Fi specification is scheduled to get an upgrade that will turn wireless devices into sensors capable of gathering data about the people and objects bathed in their signals... When 802.11bf will be finalized and introduced as an IEEE standard in September 2024, Wi-Fi will cease to be a communication-only standard and will legitimately become a full-fledged sensing paradigm... tracking can be done surreptitiously because Wi-Fi signals can penetrate walls, don't require light, and don't offer any visible indicator of their presence.

IEEE 802.11bf paper: https://arxiv.org/abs/2103.14918

Papers on device-free wireless sensing (DFWS): https://dhalperi.github.io/linux-80211n-csitool/

Remote sensing with low-cost ESP32 and 802.11n: https://academic.oup.com/jcde/article/7/5/644/5837600