Three devices released last year or planned for this one superbly illustrate the breadth of the medical profession's interests and its intimacy with electronics. At one extreme of medical care is major surgery, with brain surgery surely the most frightening. One day patients undergoing this radical procedure may take some comfort in the knowledge that their surgeon's instruments have the warp of magnetic fields for guides. At the other end of the spectrum of care is the daily checkup on one's own health, and for no one is this more important than for diabetics. For decades they have been offered implantable blood monitors, and for decades have spurned them. Also this year, another company will try to defy what many consider to be the curse of the biosensor.