Which non-Green gadgets become deepest Green when touched by a sincere Green?

Or, to put it another way, which electronic fripperies are essential to (but are seldom mentioned in) the key core Green fantasy/utopia/proscription of a world without fossil- or nuclear-powered electricity?

Speaking personally and entirely without authorization, I'd have to mention those little battery-powered timers that beep very loudly. They can stop all manner of Green-inspired enterprises going badly wrong.