Is an acupuncture mat effective for back pain?

Possibly: Acupuncture has been around for thousands of years and acupressure is based on similar principles to acupuncture. Although it may symptomatically make your back feel better is unlikely it will cure/treat the underlying cause unless due to musculoskeletal spasm/strain/sprain and the acupressure allows your muscles to relax.

No: Acupuncture is a time honored treatment for pain, nausea, energy and organ imbalance. Also it can help people with addictions who have failed to control smoking or narcotic use for their back pain. The practitioner of acupuncture can be a physician with 200 hours of training, or a non-physician with years of training. Seek someone you can work with for the duration. Maintain hope.