Hmmm an interesting one. But one i don't see a problem with. I'd have no qualms with this situation - i don't think it's invading privacy at all. It'd probably be one of these things that works for the first month then when the thieves among the airline get the message it'll soon fade out.
I have no problem declaring what money i have before a flight, if only because i work in the industry so there's not all that much to show!