Not sure about relying on the wheel friction to measure distance. What about when you are starting the measurement, from what it appears in the video the wheel will be spinning as it climbs up and over the lip before actually starting the length measurement.
Have seen these advertised elsewhere over the past few months and whilst the concept is a good one, I have my doubts about how accurate it actually is. The only way to find out is to buy one I guess.... Nah, I'll pass. They will sell thousands though, I'm sure. If it did work (accurately) then it would certainly save a lot of time measuring and marking.
I think you put your piece of wood under the wheel then slide it till it touchs your saw blade, then press the calibrate button then its calibrated
I am sure it will work out of the box for a few days, but eventually dust will start sticking to the tacky rubber wheel making slipping inevitable. MDF dust may kill it within hours. It’s funny how all the ads for tools are set in workshops that’s just as pristine as the tool !
Like a lot of stuff out there it is a "novel solution to a non-existent problem". (I first read that in a report about the Rover P6 - anyone who knows them, will know what I mean)