I have long thought that the solution to the difficulties we have keeping mobile devices charged is to make more use of the energy created by our bodies as we move around.

Once long ago I had a mechanical watch whose automatic winding worked perfectly; I never had to think about it.

Today I received news of something which is not quite that, but which still sounds useful. An iPhone case equipped with a dynamo so you can turn a handle to recharge it.

Claiming to be the “World’s first dynamo-powered iPhone case”, the AMPware Power Generating iPhone case offers up to 2 hours phone use from “10 minutes of winding”.

Let’s note that 10 minutes of winding feels like a long time when you are doing it. However, if you are stranded without power it could be most useful.

Currently the case is for iPhone 6 and 6S only. Cost is £69.99 from The Fowndry