At some point in the near future, we’ll all give up the pretense that we can live without our iPhones for even a split second and just implant the thing under the skin of our forearms. That’s the future Scosche is betting on with the advent of its new device, the MyTrek.

It’s a training device that measures your heart rate. Most pulse monitors like this strap onto your wrist or wrap around your chest. And in the realm of comfort, the MyTrek is an improvement. The comparatively small unit uses two LEDs to illuminate your blood vessels below the skin, and a photo sensor measures the flickering of your pulse.

The size of the unit and the astonishing accuracy of its pulse measurement means the MyTrek can be worn anywhere on the body. The provided strap is too long for spindly arms, so I preferred wearing it on my calf—where, I must confess, it became rather hard to take off. In shorts, it was all too easy to whip my iPhone out of my pocket and check my pulse and calories burned while I was… watering the garden. Or walking the dog. Must walk dog faster!