I made a laser guide system for my X-Carve. It works the same way as a laser guide system does for a drill press. Two laser line-modules are adjusted to intersect on the router bit. The system is attached to the spindle mount and powered by two AAA batteries. The system seems to work well with the standard Inventables dust collection system.
The 3d printed design was a bit tricky to create a relative newbie to Fusion 360. I posted the STL file and the construction details here:
The total cost for parts was less than $25, and it seems like a handy way to find a rough workplace zero at the start of your carve.
Please feel free to use, share, and modify. If you do create a system for a different CNC, I would appreciate you posting a link on the Instructable post so others can use it.