I've taken an interest in Far Infrared ("FIR") heat therapy. During an acupuncture treatment the temperature of the body drops, and FIR is a great way to keep the body warm, but also has therapeutic value as a stand alone treatment.
This Review from 2012 offers a great overview of some of the available research on the biological effects of FIR. It details studies that have shown increases in wound healing, and angiogenesis in mice, and that in vitro, FIR has suppressed the proliferation of some types of cancer cells. It also mentions studies that have shown reductions in inflammation and pain for people with rheumatoid arthritis, and ankylosing spondylitis.
As a practitioner, I find fascinating the limited speculation and proposal for future study on the vibrational effects of FIR on the nano-structured water layers on cell membranes, especially those of mitochondrial membranes.