My primary care physician suggested consulting with a physical therapist to try biofeedback, since anxiety tends to manifest in my gut, causing GI problems. Ever the skeptic, I doubted the usefulness, but went and saw one anyway.
The physical therapist I've been seeing hooked me up to a breathing and heart rate monitoring computer program that visually displays a signal of your breath and heart rate as sort of sine waves. The goal was to use your breathing to control your heart rate to have both signals synchronized, thus (theoretically) putting your body into relaxation mode.
The first thing I noticed was that I had to take very slow, deep, even breaths to synchronize the signals -- about 5 seconds from inhale to exhale. I also had to make a very conscious effort to breathe in this manner. I've been practicing my breathing during meditation for years and thought I had good breathing techniques, but the breathing required to synchronize the signals was very different, more exaggerated. My normal breathing, especially when stressed, was displayed as a shorter, more jagged signal, and could even see the "catch" reflected in my heart rate when there was a pause in my breathing.
Overall, the technique does seem to be helpful in lowering my stress level and improving my breathing habits. I purchased a hand-held device and try to use it for 15 minutes, twice a day.
FYI, biofeedback usually isn't covered by insurance and the hand-held device wasn't necessarily inexpensive. No particular endorsements here, just wanted to let people know about something I've tried.