I saw someone with a running jacket that had something like this the other day. From a distance they shone like a road sign, but as I drove past them, under the street lights their jacket looked a medium grey.

I thought this was a pretty cool technology as in my country people like to wear dark clothes, and at night they are basically invisible on the road (lots of residential areas don't have street lights). A law was brought in a few years ago that pedestrians walking at night need a reflective band, but most people don't care.