Just a note for anyone else wishing to add one of these laser pointers to their machine.
The positive supply of these devices is often connected to the metal casing so it is best to use a Delrin (or similar) clamping arrangement, as Budman has done on his mill. This isolates the device from the machine frame and will enable powering of the device direct from the BOB and switching it on and off under Mach control, as Greg has suggested, a lot easier to accomplish.
As I have used a metal clamp the body of the device is connected to ground or 0Volts therefor I need negative volts (-3Volts) to power it. This has been accomplished using the guts of a 3Volt wall wart (fitted inside my control box) which is in turn switched on and off under Mach control using a solid state relay which is directly driven by the BOB. This has resulted in more expense than would otherwise have been necessary but what the hell it's my hobby and you can't put a price on that can you ?.
Tweakie.