Each week Ross Rubin contributes Switched On, a column about consumer technology.
Nearly 25 years passed between Apple's first foray into handheld electronics -- the Newton MessagePad -- and the far more successful iPhone. But while phones have replaced PDAs for all intents and purposes, few if any have tried to be what Newton really aspired to -- an intelligent assistant that would seamlessly blend into your life. That has changed with Siri, the standout feature of iOS 5 on the iPhone 4S, which could aptly be des
