> One of my friend groups has established a nose touch as a similar (though perhaps less...rude) signal. If you have a point you'd like to make while someone else is speaking, touch your finger to your nose and keep it there. The speaking party is expected to relinquish the conversation soon so the nose toucher can speak their point while it's still relevant.

This is a great idea, although of course it relies on agreement and understanding (of the meaning of the gesture). Which you have in a friend group, but can't necessarily be relied upon in, say, a meeting with a large group.