Diesel, from the gobbledegook instructions in Chinese-English (examples given previous) I think that the screamer is actually powered by the 9v, PP9 battery that is fitted separately. I had no concrete evidence to base this on other than I couldn't see what other purpose it would serve. So I wired the Red lead to the switched supply, quite prepared for the thing not to work at all, in which case I would have rewired it to the un-switched supply and seen what happened then.
I actually think that the red is supposed to be wired to the un-switched +12v so that it can do things like flash the direction lights when the alarm is set, un-set or is going off, and also to what I can only describe as a remote engine start. There are references in the 'instructions' to this effect, not that I would dream of EVER wiring this function into a bike, or anything with a manual gearbox. Imagine what would happen if this actually worked and some bright spark had dropped the thing into gear whilst you were away????!!!!
This alarm is supposed to do a whole bunch more things than simply set off a screamer when you stand it up, and I think that this is where the un-switched +12V supply is required. It seems to work just fine on just the PP9, but we will have to wait and see how long it lasts.
I suppose the next step should really be to disconnect it from the bike battery all together and see if the thing still works...might try that tomorrow and get back to you.
One last point is that the PP9 is not a rechargeable battery, so there can't be any current coming from the box when the bike if switched off to recharge this little battery, so what other purpose could it have other than to power the screamer even if the bike battery is flat or disconnected (in an attempt to defeat the alarm).