Your friend is probably referring to a treatment called neuromodulation. The device is sometimes called a spinal cord stimulator. It is surgically implanted and delivers a low-level electrical stimulation to selected nerves in the spinal column. While its not entirely clear how it works, neuromodulation may "override" painful nerve impulses, decreasing pain. Spinal cord stimulators are somewhat more effective in relieving sciatic (leg) pain than lower back pain. A trial of neuromodulation may be considered for people with persistent back and leg pain despite medical and even surgical treatment.