i do not know of any consumer products to test for caffeine. its a chemical, and would require chemical testing supplies
and ALL coffee has caffeine, just to let you know
decaf contains minute traces though, such as 5-10mg of caffeine, far away from anything that could keep you awake or add any energy. thats about a third of a can of coke (somewhere around 30-40mg of caffeine in a can of coke)