For me, LOUD battery back-up siren is one of the best investments in an alarm system & can be readily added to ANY brand.
Especially if it's located
inside the car in an in-accessible location, they're not going to stay in there long!
My daughter's Civic was a target in her high school parking lot - when she came out after school, the car was open, the alarm module was ripped out (gone) but the battery was dead - ironic - no-one, including the school security actually reported anything amiss - but the sound of the alarm inside the car was enough to tell the would-be thieves "enough" & take off. The reality is no-one responds to car alrams going off - there are so many falses that people just don't take it as a serious threat. But it will put off a thief if its screaming in their ear!
Car Toys re-installed a new unit at no charge and re-affirmed to her that without the battery back-up siren, her car was a goner!
It takes less than a minute to find the brain usually & rip it out - same with the siren when it's under the hood - but it will still be going off even without the alarm brain so it's important for it to be IN the car and very difficult to access. (actually alarm doesn't even have to be tripped - just disconnecting the siren will set it off) There's a key switch for a bypass if you need it, so that at least has to be in an accessible location for maintenance (disconnecting your car battery will also set it off)
I keep meaning to add a second module to my own NSX probably inside the console location, or maybe inside the rear centre panel.
Yeah, I hear you "So as I say, not as I do ......"