Though not a painful or neccesarily restrictive form of bondage, I would agree with candence that, indeed, the collar in public certainly qualifies.

When I wear Master's collar out I am VERY aware of it and of its significance; more so, I think, than I would be of something that was physically more inhibiting. It's the mental aspect of the act that makes it thrilling for someone like me.

That being said, if J and I "play" in public our tastes tend to leam more towards words or phrases that are significant to us but could be taken as a passing vanilla remark by anyone that overhears. We both enjoy teasing and playing but knowing we have to wait to do anything about it. I know that strays slightly from the OP's question, as it's more mental than physical play, but I do like to keep a good thread going.