(Subscription needed sadly) http://www.newscientist.com/article/mg22129570.500-healing-s...
Read the dead tree version and it recounts a company who are building implantable devices which can be used to stimulate the vagus nerve to reduce chronic pain.
Update - Said corporation : http://www.electrocoremedical.com/
The article from another source :
http://www.bodyshox.com/blog/science/body-hack-healing-spark