

Both good options. Don’t need to be fancy, so long as it works.
Re the vibrator recommendation - that’s hilarious but apt. You want something that doesn’t move a lot, but oscillates a ton. A vibrator fits those requirements. A mechanical toothbrush could work in a pinch, but you don’t want the rotating toothbrush head, it’s the motor vibrations (offset? Can’t remember) doing the trick.
I knew a girl who once worked on a supposedly clandestine “special ops” tv show. She messaged me halfway through shooting explaining how disillusioned she was with the whole affair. I asked if, that notwithstanding, whether she had a lovely time in Costa Rica … she was horrified that I knew her location as all public releases of the tv show had them being “special ops” in Africa somewhere.
As you pointed out, Facebook Messenger let that cat out of the bag.