There are some very capable drones available for purchase. Some can carry an HD GoPro, stay airborne for an hour at a time with that payload, they can fly to a preprogrammed GPS location, hold a specified altitude, and the operator is free to operate the camera - which is sending real-time video back to the operator station, where it can be saved onto a DVR or hard drive on a computer.
They're electric, battery powered, quiet, and if you stay among or just above the treetops, they are very hard to detect, even a hundred meters distance. Upon command, it will fly back to the operator and set itself down, enabling a quick battery pack exchange, and it's back in business, back on station, recording whatever you want it to.
Cost is in the neighborhood of $30K, and to be honest, these things are amazing.
It's been reported that teams - both college and pro - have spied on opponents, it's been reported that lip readers have been used at game time, and that inside information of all sorts has been attempted to be gained.
Drones. Football. Welcome to the 21st Century.