How do they overcome safety risks? What if in the heat of a gunfight, the user pulls the trigger in a different manner and gets locked out by the gun?
It's not keyed to a specific weapon, but it seems like it would help prevent the most common dangers of either a kid finding and using it accidentally, or in an actual combat situation, being disarmed and having it used against you.
The only major benefit to per-device keying would be (marginal) additional security, and increased auditability