I am using a Raspberry Pi as the main controller for a project that will be constantly filming a video. My goal is for the Pi to stream the footage in real time to an Android device (using an app that I will develop myself). However, this camera will nearly always be used in a location where Wi-Fi access is not available. Ruling out the possibility of a standard Internet connection, what are the best ways to stream this footage to the device in real time without spending a lot of extra money?
You are using and android phone. So create a wifi hotspot on the phone, then connect the raspberry you phone's hotspot. Or you can create a hotspot on the raspberry pi itself. Try out this link Turn a RaspBerryPi 3 into a WiFi router-hotspot
It should be possilbe to send video over radio or bluetooth if for some reason you don't want to use wifi for some reason.