The safety is a good idea in theory, maybe...
It seems like it would be very convenient to have
the ability to lock a gun so it can't be used or
tampered with. Not everyone has the possibility of
having a gun safe, and while a gun safe is the ideal
way to store a gun when it is unattended (ie, while
the owner is at work, etc), if there is no safe,
then a lock like this would be the way to go,
IF...
1. It would need to be impossible to activate the
lock without using the key. This would make it
impossible to lock accidentally.
2. The lock itself should be as secure as, say,
a high-quality bicycle lock (Kryptonite, etc).
In other words, if the gun is locked, it should be
impossible to fire it or manipulate the action, except
by someone who is highly skilled or who has access
to specialized tools. This is just like a Kryptonite
lock: a highly skilled person might be able to pick it,
and a person with a grinder could open it, but otherwise,
it's not opening.
3. It should not increase the chances of jams
or malfunctions.
Given those three IFs, locks like this would be a good
option on a gun, because it just provides another
way to store it, like if you have to leave it at
home without a safe, or in the trunk of a car, or
whatever.
Designing something that meets those three criteria
should certainly be possible, but it sounds like the
Remington lock isn't it.
I'm glad that I got my 870 Marine just before they
started putting these locks on them.