I'm currently running a PbtA homebrew where secrecy between players is a big part of the story. It's early in the game and they're still circling each other, trying to figure out whether to trust each other (and having a lot of fun with it), and part of that is keeping the nature of their powers secret from each other, even when they're using them. So I've been taking advantage of the fact that everyone has their phones on them at all times, and using texts for secret exchanges, so they can tell me what they want to do with their powers, and I can give them any feedback the other players wouldn't be aware of. (I'm on my laptop using Google Voice, so I can just type, and even complicated messages don't take too long.) This feels like a big upgrade from the traditional passing-notes-to-the-GM routine in RPG — it's faster, and afterward they have a record of key game information they have and no one else has.
I also like it because it ends the problem of separating player and character knowledge. I hate games where Player X's big thing is a high perception (or insight, or knowledge score, or what have you) and the GM gives them information no one else would have access to, and the other players immediately act like they all noticed/knew that thing too. It makes the character who invested in information skills much less unique. With a lot of secret messages going around, players get to decide what to share and when, and they get to do it in character, as opposed to saying "I tell you everything the GM just said."
I'm curious whether other people use texts or email or other tech tools in their face-to-face games. (Obviously if you're playing online, all of this is much easier — Roll20 has specific tools for it.) Or whether you have other technological tools to get around game problems that annoy you. (I've become very fond of a certain Star Wars dice roller, for instance — it's SO MUCH FASTER than trying to tally up the success/fail/triumph conflicts on the physical dice.)