On February 11, 1969, Albert Dale Herman and Herbert Zeppo Marx received U.S. Patent No. 3,426,747 on a Method and Watch Mechanism for Actuation by a Cardiac Pulse:

The invention provides two watch-type mechanisms for measuring and comparing pulse rate to a standard. The coinventor Herbert Zeppo Marx was the youngest of the Marx Brothers. Zeppo replaced his eldest brother Gummo in the Marx Brothers’ stage act when Gummo was drafted into the army World War I, and he appeared in at least five of their films — mostly as the straight man.

Zeppo was mechanically inclined, and it fell to him to keep the Marx family car running. He owned Marman Products Co., which during World War II machined parts for the war effort. Marman made the clamps used to hold the atomic bombs inside the B-29 bombers Enola Gay and Bockscar. In addition to the ‘747 patent, Zeppo also patented (U.S. Patent No. 2,590,026) a therapeutic pad for delivering moist heat to a patient.