I have been using this and love it. One of the things I use it for is to remind myself in the future to do a specific thing at a specific time (I have Gmail on my iPhone, so it pings me when I get the email), but in a way that's phrased as a request from a past self (e.g. "Hi future me, Do this thing! It'll be awesome! Cheers, past me") so it'll feel like I'm breaking a social commitment instead of just ignoring a reminder.