Can't say I would ever use that specific device, but I have regularly used a similar contraption that I like to call the "jumpseat sleeper".

As the name suggests, it is only usable on jumpseats with 3-point or 5-point harnesses. You simply take a travel pillow, inflate it and place it on the neck with the inflated area under the chin. Then place a regular pillow behind the head against the flat jumpseat back. Tighten the shoulder harnesses, making sure that the lap belt does not dig into your bladder while you sleep. Relax and let yourself go!

The pillows keep your head in place, while the shoulder harnesses keep your body from sliding. Guaranteed to work!