I'm unimpressed. This is old tech. They had this figured out already in the 1960's.
The technology clearly wasn't mature yet back then. And now it's better and affordable to the consumer instead of just thsoe big gov't agencies...
BTW - is it just me - or is there a passing resemblance between Dave and Maxwell Smart?
I never would have noticed it, but now that you mention it someone needs to send him a shoe phone for the mailbag.