Mystery Gadget

I decided to dig this out of the back of my kitchen cupboard and put it to use. I should have done it weeks ago when I realised I would be at home for a very long time. Therein is a clue. Any guesses what this is used for? Answers on a postcard.

I suppose this would qualify for an ‘Emergency Blip’. (Knew it would come in handy one day!!)