IBM Research shows how health insights may come from fingernail wearable

A tiny fingernail sensor has been worked up that monitors diseases and movement disorders. IBM Research tells their prototype story in a December video. The IBM team designed the tiny fingernail sensors to help clinicians detect and monitor the progression of disease via AI analysis and grip strength. Why choose fingernails as the window to what is happening in our bodies? Two of the researchers, Stephen Heisig and Katsuyuki Sakuma, discussed this on an IBM site.
They said, "Since nails are so tough, we decided to glue a sensor system to a fingernail without worrying about any of the issues associated with attaching to skin. Our dynamometer experiments demonstrated we could extract a consistent enough signal from the nail to give good grip force prediction in a variety of grip types." Why focus on the grip? This device, attached to a fingernail, performs continuous measurement of how the person's fingernail bends and moves, in every-day activities such as opening a jar or chopping, which in turn is an indicator of grip strength. How can that reveal so much?