There are a few of us here who've experienced simply reaching for the phone, some even miming that you're calling or about to take a picture (cell phones are so small these days who can see that you actually have one in hand ) and someone leaves who you'd like to leave.

I've used mine to send myself a txt message of a plate of an aggressive driver and once .... of a very polite truck driver I wanted to commend to the company he works for