Can this Cheap LEGO RPM meter be used on FRC Bots??

[Gamer930]

Looking at the link it isn't one of the blue rotation/revolution sensors that comes in the Lego Mindstorm Kit.
I never actually played with this device or had it in my hands but what I think it is a portable device that you can just put over a wheel shaft and it gives a reading just so people can know how fast their personal creation goes :-)
My guess is that it could be used on counting rpm on a shaft that the exact same same size as the + Lego shaft. Also, probably not accurate enough for our type of application.
For us measuring RPM we use something like THIS.