Since this is current practice in the United States, we consulted the International Association of Chiefs of Police about the tests we can use to screen for different drugs.
I can't imagine what problem asking someone to track a light in a fairly dark room could possibly cause. If he can't track the light properly, his eye will jerk around, that is one of the tests.
All kinds of people can take blood pressure.
Police officers have fairly comprehensive training. They also have training to determine when there could be a medical problem. When they encounter a medical problem, they send the person involved to a hospital as quickly as possible so that real physicians can determine what's going on.
These tests are not intrusive. There is nothing I know about the tests in this program that could endanger anyone's health.