Category of devices that work offline and rarely need to charge?

There is a set of consumer electronics that are functional offline and have a very long life on a single charge or batteries, from from weeks to more than a year. Something that needs nearly no maintainance or updates. A few examples: wrist watches, e-readers, calculators, digital organizers, handheld brick game, AlphaSmart Neo word processor, WikiReader, and many more.

Is there a common name that unites all those examples?