We used a similar one once.
Our argument for why it might be legal is that it isn't a wireless communication system on its own, it is just a sensor that detects light pulses.
We would set it before going on the field and not use it during matches.
A better option we found robot-legality-wise was this:
http://www.amazon.com/HitLights-Colo...led+controller
edit:
just noticed that the one you linked uses RF wireless. that is definitely not allowed.
Our inspector a few years ago was OK with the infrared one, but I don't see them allowing that.