I have been, and still am, a fan of many Great Planes products, and this is not to bash them. But in in this case, I have to say one word... Robart.

I like the idea of a laser, but the calibration issues with that device drove me nuts, and I quit using it. You can pull the Robart meter off the wall, with or without the bar and wing thingies, and use it "already calibrated" for a huge variety of tasks... quickly and easily, and with no battery.