Interesting idea.
As others have pointed out, there are some inherent weaknesses that doesn't make it suitable for everyone.
Like one poster, I flip my pillow at night sometimes to find a "cool spot". I also tend to wake up with my pillow folded in half to support my head because I'm a side-sleeper. This pillow won't work for me.
Your literature will have to point out that a semiauto pistol should not have a round in the chamber, for safety/liability reasons. Nor should any firearm be stored inside in a cocked position.
Bad side for hotel use is that the pillow will be heavier than normal which may arouse the housekeeper's suspicions. Best to store it in the closet before leaving the room.
Personally,
I don't see a much superior advantage to the pillow over a bedside holstered gun, one in a nightstand drawer or in a headboard compartment.
Wake up, reailze threat. Grope in the dark to find the open end of the pillowcase. Pull up or down on the security flap. Reach in to find the gun, put thumb on hammer & withdraw the gun. Chamber a round w/semi-auto.
The pillow doesn't allow you to lie in bed nearly still while you draw the weapon from it's place, like a bedside holster. It is not possible to reach into the pillow while laying on it (unless you're much more flexible than I am).
Lastly... the corrosion concern. Most people's body temp rises slightly during sleep. Some of you may prespire when sleeping too. Worst of all, many people who are belly-sleepers or side-sleepers, especially seniors, may drool on their pillows at night. An older neighbor of mine launders his pillowcases (and pillowslips) every other day because of this.