Early reviews of the Harman Kardon Invoke with Cortana -- the smart speaker that features Microsoft's personal assistant -- have been lukewarm at best. The speaker will be available in the U.S. starting Sunday. Like Amazon's Echo line and Google's Home speakers, Invoke lets users play music, manage calendars, set reminders, check traffic, get news reports, and control other smart home devices. The Invoke lets users tap Skype to make calls to smartphones, landlines and other Skype-enabled devices.