In 1951, his health worsening, Woody Guthrie flipped the switch on his new T-100 reel-to-reel tape recorder to lay down several songs for his publisher. His days as a recording artist were done.

A quarter-size device that tracks the rise and fall of sugar in your blood is the latest source of hope — and hype — in the growing buzz around wearable health technology.Continuous glucose monitors,