BAC is a well understood thing to measure, but marijuana testing seems pretty unreliable to me. I’ve read conflicting reports about how strongly TCH found on a saliva swap correlates to actual intoxication, and I don’t believe there’s been much scientific investigation done to determine what levels of intoxication are safe for what activities. As the primary customers of these products are law enforcement, and private sector “rules enforcement”, I’ll remain skeptical of them until somebody manages to convince me otherwise.