A piece of hardware you may have never considered if you are security conscious

A handheld RF spectrum analyzer is probably your best friend and possibly a RF jammer. It's now cheap and easy to broadcast radio signals to take advantage of the piezoelectric effect in IDTS and listen in on what is happening in any given location. A small number of HAM radio operators have been able to do this for decades but it is now becoming cheaper than ever to do this. My company (a major bank) was able to independently verify this is possible and we're now in the process of finding out ways to mitigate the problem without going into the tinfoil hat realm.