Active firearm safeties have not became a reality because of a limitation in technology. The ability to transmit signals a short distance can be done with IR, RF, sonic and visible light even in a very small size. So an authentication key, ring, badge, holster or other device could be used to release or activate a safety in a firearm. The issues are expense, maintenance, and failure recovery.
This design is an active magazine safety. By incorporating the battery, electronics and a ammunition retaining device into the magazine, there is no need to modify an existing firearm. The electronics can be activated when it senses that the magazine has moved, or removed from a holster, then if the authentication device is near either activate or deactivate the retaining device. This disables the use of any ammunition in the magazine. An authentication device could be anything as simple as a ring or badge with an RFID tag, or a custom credit card sized transmitter. Firearm manufactures may want to include a safety switch in the magazine chamber to be triggered by this type of magazine.
By using existing firearms and not requiring any modification to them, the expense is greatly reduced. Maintenance is simplified by making all active components in the magazine, eliminating the need to take the firearm out of service for something like charging the battery. Failure recovery: if the safety fails to release, the procedure would be the same as an empty magazine, something with which every firearm user is familiar.