Magnetoception, the ability to sense magnetic fields like a compass, is my prediction for the first widely implemented super-sense, because it’s so simple.
I’m no biologist, but it certainly seems that only a little wetware is necessary to implement magnetoception, since even bacteria have it. On the mechanical front, tiny manometers have been built into millions of devices already. I have no idea what the state of the art is, but the first 3-axis digital compass chip I found on google measures 4x4x1.3mm. They’re only getting smaller and more efficient. We already have the technology to build it into belts and clothing.
But I hope I’m wrong. Certainly, the future promises more than better compasses.