I've been using reflective bike vests with waistbands forever. A few years ago I added 2 Planet Bike blinkies to the waistband, one at each forward corner of my hip. They work. It is very obvious that drivers see them and wait to see what I am going to do. Soon after I started using them, I rode home in the dark having forgotten my headlight. Two left turning drivers waited for me to clear intersections.

Ben