If it works, the GoBe will be life-changing. But it’s a big if.

The GoBe is a bracelet that looks like a small microplane has been affixed to a black watchband—the top of the microplane is a display, and its underside is a sensor. Through its “patented flow technology,” the GoBe promises to measure the wearer’s heart rate, calories burned, sleep, and stress levels. That’s all conceivable, given what the FitBit and other body trackers already measure. But the GoBe also promises something a little more sensational: Automatically tracking the calories of everything the wearer eats, through his or her skin.