I seen this on Drudge report. It doesn't surprise me that they're testing it. I've seen a lot of that sort of thing when I worked at Yuma proving ground. It's a great idea since every long range ballistic missile is GPS guided and with Iran, and n Korea testing missiles on top of China and Russia putting around off the coast of California in nuclear subs...
None of our strategic ballistic missiles are GPS guided. They all rely on inertial guidance with stellar observing to assist and correct for drift. Unless someone knows how to turn off the stars and negate the laws of physics, ours are un-jammable. The Trident D5 is accurate to 90 meters, the Minuteman III is accurate to 120 meters.
I am certain the old Soviet designed strategic ballistic missiles have the same type of guidance, as they were designed long before there was a GPS. The Russians haven't changed the concept of their guidance, since they actually don't own a GPS constellation.
Same goes for the Chinese. Of for that matter the Indians, Pakistanis, Iranian and even Kim Jong-un...
The problem isn't the strategic threat, think smaller . . .
(you can buy GPS guided drones that can fly, without human intervention, along a pre-planed route, with up to 125 waypoints. Imagine the possibilities....)