Satellites can bounce LASER light off of your windows and, by measuring the minute distance differences between a vibrating window and the satellite, reconstruct your speech -- from orbit! I don't know how much this process costs yet it was demonstrated for PBS some years ago so it may not be all that expensive. The quality of the audio is poor but it can be understood.
Given Moore's Law and the dropping costs of high technology, it's not all that far-fetched to imagine that this sort of thing is now being used on deadbeat dads and people with overdue library books; or if it isn't, will be soon.
Secondly, a somewhat more academic and less Loompanicsesque paper on surveillance techniques and countermeasures, with a catalogue of 11 types of strategies against surveillance:
A common form of switching involves certification transference: A ticket, entry card, license, entitlement or identity marker belonging to someone else is used. South Africa provides an unusual example. There, welfare payments can be obtained from ATM machines. The recipient enters the correct information into the computer and offers a thumb print for verification. A colleague reported one enterprising family that collected welfare payments long after an elderly relative had died. They cut off her thumb and continued to use it.
A more subtle form involves conversational ploys in which a surveillance agent is duped into believing that a machine is invalid. Consider the story told me by a Russian. A family coming back from a picnic is stopped by police and the driver fails a breathalyzer test. He protests, "That's impossible, I haven't been drinking, your machine must be broken. Please try it on my wife." She also fails the test. The man gets even more insistent that the machine is broken and says, "Please try it on my young daughter." She is tested and also fails. At which point the police officer, doubting his own machine, lets the man go. The man later remarks to his wife, "That was really a good idea to let her drink with us.
Writing in invisible ink is a familiar children's game and it has its' adult counterparts, although these may rely on bad science. Thus, a bank robber was identified and arrested in spite of rubbing lemon juice on his face because he had been told that it would prevent the surveillance camera from creating a clear picture.
(Of course, these links are provided for the curiosity and interest of law-abiding readers only. If you're an al-Qaeda terrorist, drug user, MP3 pirate or other criminal, please do not follow them. We thank you for your cooperation.)