It’s been a long time since my last free idea, even though I’ve had a few knocking around my head for even longer. Still, worth the wait I think, this one is a corker. And it has nothing to do with burning my hand on the kettle at work trying to find out if it’s hot or not. Honest

Simple: A sticker, that changes colour to heat (they exist, used to come free with cereals) but more specifically only changes colour when its above 85-90°C (arbitrary numbers right now but hey). You then stick the sticker to the side of your kettle. If it’s changed colour, no need to re-boil.
Tefal could do a whole thing about it, seeing as they have the frying pans with a similar idea.

Or, if that’s too simple and cheap for you. A kettle that has a ‘recently boiled’ light on it, that’ll stay on for 10 mins after it’s been boiled.

Someone please do it, and if you feel the need to celebrate my genius with this simple thinking then mail me: rob AT randomtask DOT co DOT uk.

(I’m sure you can workout the anti-spam action going on there)