The ARB solution for controlling the locker is a compressor unit, solenoid unit, compressor switch, locker switch and wiring harness. The compressor kit (compressor, compressor switch, pressure switch and wiring harness) will cost upwards of $400. The locker switch and solenoid come in the box with the locker.
The compressor unit is a motor, compressor, air tank and manifold all in one. The compressor is controlled by the pressure switch. The solenoid unit is two pieces, a valve and an actuator and is controlled by the locker switch. The pressure switch and solenoid unit are mounted to the manifold.
The way it works is very simple:
The compressor switch turns on main battery power. If the pressure in the tank is below the lower limit of the pressure switch the compressor will run until the tank pressure reaches the upper limit. When you turn on the locker switch the solenoid opens the valve to the air line which in turn moves the sleeve in the locker. When you turn the locker switch off the solenoid de-energizes and moves the valve again, dumping the pressure from the line side while simultaneously blocking off the tank side (this is where the familiar psshhtt sound comes from). If you turn off the compressor switch before the locker switch it de-energizes the system and again the valve dumps line pressure.
Note:
The switch for the compressor is because the tank leaks. Originally there was no off switch for the compressor, it relied upon the pressure switch and excessive run time caused the compressors to fail prematurely. ARB solved this problem by allowing you to turn off the compressor when the system is not in use.
The main complaint about the ARB system is the fairly common failure of the solenoid and the short duty cycle of the ARB compressor. Also the small size of the ARB compressor's integrated tank means that in the event of a leaky system the compressor will run more often and for a longer period. The ARB blue plastic lines are prone to failure because after a while they get brittle and split (like when you break a straw trying to get it out of the damned paper wrapper

).
There are many different compressors available that are both more robust and less costly than the ARB compressor. In vehicle air tanks can be found in many sizes from about 1/2 the size of a medium sized juice jug to large enough to run air tools off of. The bigger the tank the more compressor you need. Mechanical air switches like those used on big rigs are cheaper than solenoids and are rock solid reliable. A switch and relay rated for the current draw of the motor can be purchased at any auto parts store. Pressure switches are readily available for about $20 and a small manifold is available for less than $10. Rubber air lines are more durable and easier to work with than the ARB plastic line. As well you can buy expensive (but in my opinion uneccessary) braided steel air lines from several aftermarket sources. Throw in a few miscellaneous brass fittings and you are all set.
You can expect to save at least $100 by doing it this way and at the same time end up with a more reliable system. As well, should something go wrong it is cheaper to repair.