It'd be hilarious if it were a passive listening device like The Thing, but Trump seems so attention-hungry and security-oblivious that you could probably just leave a big microphone on his desk like an old-timey chat show.

https://en.wikipedia.org/wiki/The_Thing_(listening_device)

I thought of that, too. Surely they wouldn't be that bold, but then again, it's such an obviously crazy idea that it might just work.