The device on the belt Jin wore was called the 'System Driver', (for lack of a better name from Jin). It had been personally named like this by the System as it had created it instead of waiting for Jin's researchers to build it.
It was basically a replica similar to what all the various masked heroes used in TV shows to gain additional powers, only that the System was able to do the same for Jin without resorting to cinematic tricks. (Perhaps, the System itself wanted to copyright such a design and enhance such powers for its own benefit?)
Unlike those TV shows, the System Driver was authentic and not some dungeon instance magic fabricated by digital ones and zeroes. Yet the design and concept worked the same. Jin had an activation device to transform, and his phone acted as the key for this. The System would transmit the data and pieces of armour it had stored within the device to equip Jin almost immediately.
