Found some more information at this page:
http://www.combatcentral.co.uk/notes_bfg.asp
He says that the actual time on the grenades is around 2 seconds or so (seems bout right in the video). I've heard a lot that the time can very between 4 and 2 depending on how much you lubricate the timer (or how much dust you get in it...) though i'm not 100% sure how time timer works, this would make sense as it has to be mechanical of some sort.
Also, this would be an awsome product to have here in canada:
http://www.combatcentral.co.uk/produ...ls.asp?PID=132
Trip wires! Man those would be fun.
These may be patented, but most likely they wouldn't be in canada (probably UK and the US maybe) so you could base your design off of them.
These grenades take away the bad part of pyro type grenades (storeing/selling/shipping non-standard and dangerous explosives) and keep the fun parts (the loud bang!).
About the legality, when i talked to customs about it they didn't give me a "Holy hell there is no way that is comming into canada!" it was more of a "Hmmm, well they seem alright, but you should get a ruleing first". As such, who knows, they may be legal to import (or even manufacture).