This just feeds the illusion of security. If they are that concerned about electronic surveillance, there is a lot more to consider.
Does the room have electronic countermeasures to protect against the cabinet member that forgets to leave his phone/watch outside?
Google is your friend
https://www.bvsystems.com/product/wolfhound-pro-cell-phone-detector-bundle/
https://www.bvsystems.com/product/mantis-bluetooth-security-sweeper-bundle/
I actually got the chance to play with one of these in a trade show
http://www.keysight.com/en/pd-10000...tion-system?nid=-32860.536880593&cc=US&lc=eng
I like how everything is an "illusion" of security if people don't like it. If you don't have a policy banning electronic devices, what are you going to have? Everybody is free to bring whatever they want into a secure area? Is that more secure somehow?