Onusblue from Derma-Tec

The patch changes colour based on the level of drug detected

They’re using this for alcohol at the moment but the possibilities are massive>>>

http://newatlas.com/onusblue-color-gradient-alcohol-drug-detection-patch/46584/?utm_source=Gizmag+Subscribers&utm_campaign=5d70b80327-UA-2235360-4&utm_medium=email&utm_term=0_65b67362bd-5d70b80327-91677545