I mean, look at it. They’ve obviously designed it after tank treads, and it looks like it could take a beating and keep your 2.5″ external drive (like the Rikiki Go), Nintendo DS, camera, or Pokeball intact. I don’t think it can be submerged, but it could certainly take a splash.
£20 (probably $30 US) is a lot to pay for a box, but if you travel a lot, it might be a good idea. Think of it like the hard cases photographers and other professionals use to keep their gear safe.