A tethered balloon would make a good temporary observation point for rocket launches.  If the tether breaks, you're in a tough spot though.  It would need a deflation valve.

The practical version would be unmanned & have a high resolution camera.  It would have 3-4 tethers to keep it reasonably stationary.  It could capture sound without the noise of a quad copter. 

Another idea is using the platform to launch gliders.