Pro photography shops carry a spray meant just for that. I think it's called dulling spray. You spray it on glass objects so the flash doesn't cause those nasty reflections. Unlike sandpaper, the effect is reversible.

Also, several outdoor shops carry watch bands that have a Velcro flap that fits over the watch. But, IMO Velcro makes too much noise. You can't check the time without causing that nasty Velcro ripping sound. You would be trading visual signals for audible signals.