having seen this type of stuff (not necessarily this specific product though) at the bike shows in the past and taken pics with a digital camera - I wouldn't be buying based on my results - could see the plates as clear as day.
I seem to remember one of the mags did an article and published the photos……….. nuff said really.
That's the image that sticks with me too. A trader's stand with loads of plates all apparently coated with the stuff, all clearly displayed on the cameraman's flash photo.
in the old days it probably could have worked, however the scamera's are now pretty much high end digital and have enough latitude to draw out the most scant on info and details.
the slave flash gun idea did have legs but again with digital the only sure way is to either....
having noticed your number plate fell off and be on route to a place to have it fixed back on.
forget that you number plate may get covered in thick mud/ road dirt
or slow down
but if they catch you you should take it like a man and write an article on here about, whinge on about it for ages... If you could add some video that would be good too...