When I used it to open a jar, Holly came running. Not so much because of the contents, but because the sound is similar to her ball launcher!
This works well, but only on some jars. You'll need a back-up, like this Boa Constrictor Strap Wrench, or like the one that Maarten gave to me. It's rather fitting that this looks like the nose of a spaceship, right Maarten?