When playing blitz or rapid games, if your phone is on silent, you don't realize when you're running low on time because the only warning is an alert sound. It would be great if the phone vibrated when there are X seconds left, similar to how Chess.com does it.
That makes sense! Personally, I also find it hard to play with my phone on silent, because I need to hear when a piece has moved. A vibration warning when you’re low on time could definitely help players who keep their phone muted... or at least scare them a little, haha.
On an android phone, it should be available in the hamburger menu. iOS Safari does not yet support vibration api.