Another device I loved in fiction was the marvelous hat worn by the Golux in James Thurber's The Thirteen Clocks. That's an image of the Golux up there, wearing his fine example of haberdashery. The Thirteen Clocks is one of the most wonderful books ever written for a young audience. If you haven't read it, you should. It's out of print these days but you can still find used copies on the net. (And the fact that I refer to a "device" in reference to the Golux is an inside joke. At one point in the book the Golux says, "I am the Golux, the only Golux in the world, and not a mere device.") Thurber was so playful in this book. The language is fresh and interesting and great illustrations accompany the text. (I remember reproducing them in pastels in my teenage years. These are magical illustrations.) Literate adults should enjoy the book as much as, or more than, adolescents. I'm sad it's out of print.
The Golux is a unique character in literature and if you do get a chance to read the book, I think you'll love his hat as much as I do. It was just a quirky addition to a character's outfit, but because it is quintessentially un-understandable (i.e., the hat makes no sense), it adds to the mystery surrounding the Golux. It is indeed a device.
I've used a few devices in my books. I hope at least one worms its way into the hearts of readers. That would be grand.
PS: Pardon the inclusion of a graphic today but the post would have been senseless without the image. Anyway, it was tiny. Sorry, dial-up guys.