Back from vacation, having flown a Boeing 737. This lacked the personalized screens seen in longer haul craft but it had a headset jack and a set of volume and channel controls for each passenger. The controls were set in the armrest, in easy reach of the passenger, like this:

Boeing B-737 armrest audio controls

Cool, huh?

Not cool. The two rocker switches for the volume control and channel selector are flush with the surface of the armrest. This means that if you rest your arm on the thing – or if your neighbor in the next seat does – your channel is bound to skip up or down every few minutes. If you watch a movie this can get truly aggravating.

And all they had to do was recess the controls a couple of millimeters under the surface…