Well I built the thing.

Pros:

"Construction" is easy. Connect the clips to the ends of the cell and you're done.
It's cheap if you own a meter.
It takes up no room. It will fit with my meter.
Calibration once I figured it out was easy.

Cons:

it's dark in the darkroom. The problem is the meter is hard to read in the dark. I ended up using a flash light to read the meter.
I'm not sure if it works. I used it to measure a clear section of an old negative and got 0.643. I guess that's fogbase?

I'm thinking of ordering a stouffer transmission wedge [yes finally] maybe that'll help me figure out if it works.