Ah, it is aka biofeedback. I hadn't heard of neurofeedback before.

Yeah I've heard of it mostly in terms of stress. They did studies on biofeedback for guys who were at risk of heart attack. They got a 'beep' warning when their heart rate went up and they learned strategies for reducing their heart rate. To teach them to become more aware of the state of their heart and do something about it, basically. They had good results.

Yeah, you can use it for other things (like anxiety) too. I find that doing mindfulness meditation nightly teaches me to be much more aware of how tense I am feeling during the day. The nightly practice also means that it is much easier for me to do something about it (ie relax) once I have become aware of it. Can use it to help regulate intense emotional responses too.