This is a costume prop I made a few years back when we went to Phoenix Comicon. I wore my suit, grew a goatee and went as Tony Stark. Of course, you can’t do that without an arc reactor! This one went under my shirt and involved a few LED’s and resistors, an old belt, a bit of styrofoam and cardboard, a scrap of acrylic and 9V battery. Total value of materials was about $5. Worked REALLY well under a dress shirt!