That's a bang-up idea. The fun would be to get a realistic assault rifle replica (maybe an Airsoft) and build in the electronics. Might attract the local cops- be sure you have an orange tip for the barrel.
I wonder how wide the beam is, and the range? It's not exactly fair to broadcast a wide "shotgun" signal. No lens is mentioned, and a simple apeture (pinhole) is just going to kill the amplitude.
I guess it's a problem with all laser tag, but it looks like the killing area gets larger, not smaller, with distance. And close range may have trouble hitting the sensors due to the small beam radius.