Breathalyzer or drunkometer.

Breathalyzer /brethalaizer/ or drunkometer (AmE) - it's a device to meausure the alcohol level in the blood. - Alcoholímetro (SP) - bafômetro (PT).

Example:

If you drink a beer, drive a car, and you are tested with the breathalyzer you may get into trouble. - Si tomas una cerveza, manejas tu coche, y te analizan el aliento con el alcoholímetro puede que te metas en problemas.