I have similar magnets and I decided against using them for a few reasons. The big one was I planned on doing a fair amount of rock crawling and I didn't want my handgun bouncing on the floor. Another concern is the slide getting magnetize and messing with the function. I never researched it...
When I go to the beach I put the key in a faraday pouch and put that in my gun lock box under and attached to the seat. It's a fingerprint reader and works very well. Now I don't feel like I need to watchdog my Bronco the whole time. I've left it with the doors off a few times as well.