NEW YORK - At least half a million New Yorkers have diabetes, many of them at risk for blindness, kidney failure, amputations and heart problems because they are doing a poor job of controlling their illness. The question is, how much privacy are they willing to give up for a chance at better health? A century after New York became the first American city to track people with infectious diseases as a way to halt epidemics, officials here propose a similar system to monitor people with diabetes, a non-contagious foe. Conceived after a sharp rise in diabetes deaths over the...