Very clever indeed...
I must agree, since I bought the very same digital voltage meter! I have to admit that I'm jealous of your lighted rocker, you found a much sexier switch for yours.
I spent a little more overall because I'm building mine in a project box... I didn't want to put a hole in a bulkhead for it, I'm going to attach it with adhesive (at least initially) above one of the reading lights on the street-side bulkhead that walls off the bathroom. I'm going to tap off the light for the voltage reading as long as having the light on doesn't affect the reading too much. If I have to run a line for the voltage I'll tap off the fuse block, which is in the closet on the other side of that bulkhead.
I set mine up with a toggle switch for constant-on, and a momentary button to take a reading on the fly so I can switch it off to conserve those few milliamps when I'm on battery power, and have it on to monitor the converter voltage when on shore power. I put a fuse inside the project box as well, just for extra overkill.
I haven't installed it yet, so the display is dark, but it's clearly the same display, I recognized it instantly.
Nice choice! The matching blue light on your toggle is just perfect, I may have to upgrade to that switch later.