BERKELEY, Calif. — He could have been surfing in Cabo. Instead, Tyler Crouch, then a 21-year-old mechanical-engineering student, spent spring break of 2013 building a digitized stethoscope and thinking, “This better be worth it.”

Since then, he and two classmates from the University of California, Berkeley, have formed a company — Eko Devices, which is based here — raised nearly $5 million and sold 6,000 digital stethoscopes, used in 700 hospitals. The wireless stethoscopes can transfer a patient’s heart rate and other vital signs directly to Eko’s secure portal, where it can, among other things, be shared with other doctors for a second opinion.

Now they have built something with a potentially larger market: It is the Duo, a digital stethoscope for home use, which could change how heart patients are monitored, the entrepreneurs say. It is scheduled to become available by prescription in the fall.

The product, which fits in your hand, combines electrocardiogram, or E.K.G., readings and heart sounds into a device that allows patients to monitor their health at home and send data to their physicians.