First I just wanted to say that I have no idea who came up with this mod in the first place and what I am about to show was inspired by Black_Rose and is based on what he had previously posted.
 - credit goes to KoolMoeCraig for coming up with this mod - thanks for the idea.
The purpose of this is to add blue LED flashers to the cabinet, I added mine to the top. The wires for the lights feed into the back box via the grills on the back.
Module prepped. I wanted to use some Molex connectors vs. just splicing in the power so I crimped on some pins. Male 0.093 pins at the y (red circle) and female pins at the other ends. The tie wrap was part of Black Rose's documentation for selecting which mode you wanted displayed (I wanted A flash 3 times one side and then 3 times opposite side and repeat). I later decided to modify the module to eliminate the tie wrap as IMHO it didn't look very nice. The unit has no memory, so the switch has to always be pressed so that your selected mode is active when power is applied.
To modify the module, all I did was basically short out the A switch inside. Bottom cover removed. The 2 pins that are circled are where the switch closes the circuit on the board to select A mode (screw driver points to the A button).
I just added enough solder to bridge the pins that are circled above.
Here is where I screwed the module in the back box. BTW the wires for the lamps on top I have passing through the grill - they will not fit as is, I removed the pins from the housing (paid attention to which one went where just in case) and passed the wires through and then reinserted the pins back into the housing.
The power was taken from the beacon supplied power (which is AC, but the module has a rectifier inside to convert it to DC so all is good). Here is a close up of how I have the power hooked up. Basically I picked up some 0.093 Molex connectors and pins to make it look 'neat'. Basically unplugged the Beacon from the resistor board and inserted the module.
Basically, the blue LED lights flash any time the beacon is on.