In the latest attempt to fulfill sci-fi movie fantasies, tech firms have been lining up to provide you with a virtual assistant. From well-known voice-powered AIs such as Apple's Siri to upstarts like Viv, the goal is to quicken the actions you already take on your phone and other devices, growing ever-more efficient at the job by learning from your behavior. But like any hired help, each of these AI assistants has different skills, blind spots, and quirks. Bio: A voice-driven assistant that talks back to you--invoked by long-pressing the iPhone or iPad home button--and proactively recommends actions to take. Recently took up residence on Apple TV and Apple Watch.