When his chemotherapy patients leave the hospital to continue treatment at home, Edward Greeno faces a new challenge.

He can no longer ensure they’re taking their medicine.

Greeno, the medical director of the Masonic Cancer Clinic at the University of Minnesota, has come to realize that some patients, like children hiding naughty behavior from a parent, will fudge the truth to avoid his disapproval, even when their health is at risk.

To combat patients’ fibbing and forgetfulness, Greeno has begun deploying a new tool in recent months: a pill embedded with a tiny, ingestible sensor. The sensor transmits data from inside the patient’s body to a wearable patch placed on their abdomen, which then connects to a mobile app that patients and doctors can access.

That data offers a new window into patients’ health and behavior, Greeno said, allowing doctors to remotely monitor someone’s heart rate, activity level and sleep cycle. The sensor, which is about the size of a grain of sand and dissolves in the gastrointestinal tract, also tells doctors when a patient has ingested their medication. The information is compiled in a database that doctors can access from their devices.

At the Masonic Cancer Clinic, as part of a pilot program, doctors have begun pairing the sensor — made by a California company called Proteus Digital Health — with a common chemotherapy drug used to treat stage 3 and 4 colorectal cancer patients.