802.11bf Wi-Fi 7 Sensing works with all frequencies, 2.4 and up.

Even if Neighbor 2 turns off their router, Neighbor 1 could passively use the radio waves from Neighbor 3's router to surveil reflections from Neighbor 2, including keyboard typing, heartrate/breathing, location and physical activity.

Previous discussion: https://news.ycombinator.com/item?id=27123493