This is not only less invasive than a blood sample, it's potentially much more practical. You can't always take blood (a pilot isn't about to try it mid-flight), and it's not realistic to monitor blood continuously. With sweat, that's not a problem -- the scientists could track electrolytes for up to five hours at a time. That could be vital for tracking conditions where you need continuous data, such as the performance of an athlete, stress levels at a high-intensity job or a recent surgery patient.

The best part: this may be a practical reality sooner than you think. One of the researchers co-founded a company, Eccrine Systems, that's in the midst of refining and commercializing the sweat-inducing sensor. There's no guarantee that you'll buy one off the shelf, but you may eventually wear it when some future doctor or coach needs your health stats.