I use the Satechi Bluetooth Button Series Media Button with my iPad for this same purpose. When I travel, I will sometimes watch movies on the iPad hooked up to the hotel TV, but don't want to get up to change the volume, etc, so I use the button for that. Looking at the answered questions on Amazon, it looks like it works with Macs as well. Should do exactly what you need, and it's much smaller than an iPhone. If you do get one, I'd suggest attaching the lanyard it comes with. I don't actually use the lanyard to carry it around, but there is no way to tell top from bottom without it as the device is round. Using the lanyard, you'll always know which side it up, so you can use it without looking at it.