There's a decent caled a "pot watcher" (aka: boiling-rattler) that is a mechanical "hey, it's boiling" indicator.
Anytime I'm cooking or thinking of cooking, I'll always throw water into the tea kettle (countertop boiler) and start it off, for exactly the reasons stated.
I'm very thumbs up (and already follow) almost all of his advice, including the "use two boiling elements to get water boiling faster".