Alexa on your smartwatch?

Alexa-enabled speakers like the Amazon Echo (which is still on sale at its lowest price of 2017) and the Echo Dot are terrific, but they're inherently limited. What happens when you're in a room without an Echo speaker? What happens when you're in the back yard? What happens when you're in the car? What happens when you're anywhere other than the one or two rooms where you keep your Amazon speaker?