One of my clients carries an echo dot with a battery pack with her when she's in her back yard, gardening. She mostly uses it for music, but the ability to drop in/phone call if she falls an can't get up has been a real benefit to her peace of mind.
FYI for the interested, and I admit a data point of one, but tp-link's Kasa stuff have been the most reliable of the smart switches, plugs, and bulbs that I've tried. Never once had an unexpected desync with any of it.