Good point, there is an acceptance that as long as a device is rechargeable it is 'green', although it may have a net power consumption that would be unacceptable if powered from a primary battery. Transferring these devices' smart power-saving tricks to battery-powered devices might be something we will see, but we need a new, greener primary cell first.
Some fuel cells look interesting there, some claiming to be recyclable.
Professionally, I am concerned about the EMI background noise floor rising at a measurable rate, as you point out.
Replay available now: A handful of emerging network technologies are competing to be the preferred wide-area connection for the Internet of Things. All claim lower costs and power use than cellular but none have wide deployment yet. Listen in as proponents of leading contenders make their case to be the metro or national IoT network of the future. Rick Merritt, EE Times Silicon Valley Bureau Chief, moderators this discussion. Join in and ask his guests questions.