Using a spotting scope or even binoculars can be a hassle, especially if you wear prescription glasses. To that end Double Gripper Phone Adapter by Novagrade is a huge help. It allows you to attach your phone to most any spotting scope or binocular.
This lets you view through the much larger screen on your phone, without having to bring the optic to your eye. This is an obvious benefit if you wear glasses, but is also very handy if you want to take photos or videos through the optic. Not to mention the ability to quickly and easily show someone next to you a point of interest. Overall I am pretty impressed with the Novagrade Double Gripper.
You can find the Double Gripper here.