i am not expert, but i'm curious.
one of modern dangers is use of personal information to blackmail, satirize or compromise someone.
that's where attackers use surveillance devices.
it's called 'technological surveillance'.
surveillance methods include:
- use of mechanical devices,
- direct visual surveillance attacks,
- use of electroacoustic transducers (microphones of various types),
- wireless emitters of various types - not only WiFi,
- radio-frequency over electric circuits,
i'll elaborate as soon as i can.
-- Based on 'Taktyka działań ochronnych. Ochrona osób.' by Jarosław Kaczyński.
-- i've added a little of my opinion as well.
See also, if You wish: Wiretapping.