Although excellent medical care is always in high demand, the healthcare sector continuously evolves. Companies aren't automatically worth investing in just because they provide essential medical services. Only those that can keep up with the changing nature of the industry can hope to deliver excellent returns over the long run.There are many such stocks on the market. Let's consider two that specialize in developing medical devices: DexCom (DXCM 0.20%) and Intuitive Surgical (ISRG -0.66%). These healthcar ...