Man Wakes Up With Mysterious Device On Wrist, Regrets It When He Takes It Off

Seeing the device

I looked at my wrist and saw a small metal device. It was clamped around my arm tightly, so much so that my arm bulged around the edges a bit. I had never seen it before, and as far as I knew, I did not sleepwalk during the night. So how did it get there?