I'm curious if you can set up the mobile key on a android and then order the physical key later and then use it too? I am always misplacing either my phone or keys and would like to have the ability to use either to login with.
No. The two are not * interchangeable*, and you can only associate one or the other with your account at a given time.
You can however freely switch between the two at the SWTOR website, but you'll need to have both devices (your smartphone, and the key fob) on hand to switch between them. (i.e., if you wanted to use an Android device for now while you wait for a physical key to be shipped.)