You can use a video transmitter to send the live signal from the GoPro to a ground station where you can use goggles to see what the aircraft sees in real time. Quality depends on what transmitters you get, as well as a few other things. It's quite common actually, just search for FPV RC.
You can take it a step further and incorporate pan-tilt mechanisms which let you control the direction of the camera. With some programming and GPS, you can have the camera geo-referenced so that it will continue pointing at a certain target on the ground. Similarly, you can stabilize the camera.
Here's a picture of an aircraft which was designed around autonomously spotting targets on the ground using a GoPro with a pan-tilt mechanism: