thats a major lawsuit wating to happen IMO. arrest them under suspiction of driving while intoxicated and take them to the hospital or jail and let it be done in a safer enviroment other than the side of the road.
but i agree that if this could happen if you were to be pulled over it would cut down on the amount of drunk drivers. they would know that even if they could fool the breath test they would have to be checked by a blood test that isnt going to lie.