What is really interesting is that sunlight naturally has the 660nm light in it. Take a look at the distribution of wavelengths in sunlight from the graph below:

Image from http://solarjourneyusa.com/sunlight.php

Basically this means just going outside and getting some sun can help heal your wounds quicker.

WARNING: Although going out into the sun for healing purposes is good, sunlight also contains harmful UV rays that can burn and damage your skin. Therefore having a device that outputs just 660nm light could be better for you in certain situations.