Have you ever been a passanger in a car and wanted to have a sleep. If you take a pillow and lean it against the window it always ends up bunched up and your head ends up hitting the window. I think that if you put plungers on the pillow (so that it would stick to the window) it would help prolong the sliding down of it, meaning that you would get a longer sleep.
A very simple idea, not sure of the market though.
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