This is scary. Really scary.
You don't want to be free do you?
I can remove an eyeball with my pocket knife.
Because the technology is available, it will have to be used.
Of course I want to be free. I want to be free to drive home late on a Saturday night, and not worry that a drunk driver is going to weave across the center line and hit me head on.
As long as the results are not provided to law enforcement, there is no constitutional issue here. The devices should neither record nor transmit the results. If they do, I'll be on your side fighting like hell.