Apple CEO Tim Cook has been spotted testing a glucose monitor connected to his Apple Watch, according to unnamed sources at CNBC:

Tim Cook has been spotted at the Apple campus test-driving a device that tracks blood sugar, which was connected to his Apple Watch. A source said that Cook was wearing a prototype glucose-tracker on the Apple Watch, which points to future applications that would make the device a “must have” for millions of people with diabetes — or at risk for the disease.

We already knew Apple was working on this technology, and Mr. Cook himself said earlier this year he’s been testing one. But the new report suggests whatever Apple is working on is advanced enough to be tested in the wild, or at least the wild confines of 1 Infinite Loop.