This is an amazing concept and while the Dastardly & Custard lemon-powered torch is only an idea, the Japanese have invented a water-powered torch.
It is called “The NoPoPo Mini Lantern” and is only $38. I won’t blind you with science (you can blind yourself with the ‘read more’ link), but the fact it will run for up to ten years is awesome. Particularly handy in the UK with all the rain!
Implications - Consumers are looking for products that complete more than one function. Items that can multitask with efficiency are appealing to those who have fast-paced lifestyles. Companies trying to increase their popularity could focus on this.