Yep - that's on it's way ;-) At this point, having such a 'check engine light', or, for instance, having a cluster of 10 cells under your wrist that change col

Yep - that's on it's way ;-) At this point, having such a 'check engine light', or, for instance, having a cluster of 10 cells under your wrist that change color (which is subsequently sensed by your iWatch) is just a (very challenging and expensive) engineering problem. It's entirely scientifically reasonable to have such biological readouts sensing a number of different biological states. You already blush, perspire, increase heart-rate, etc. - hooking up those same responses to change the pigment in 10 particular cells on your wrist is not much of a stretch of our current tech. It's only logistical sci-fi, not theoretical sci-fi.