I had the previous Gorilla model on my TW some time ago. It works great, except the range of the pager isn't all that great. Even 30 feet away inside a building was pushing it a bit. Also, it's bulky enough that it would be a bit of a pain to fit on the FZ. Not impossible mind you, just difficult. The good part about the alarm, is the shock sensor works really well. You can set it so if someone were to just lightly touch
any part of the moto, and it will sound a brief "warn away" siren. And it's quite entertaining to watch co-workers trigger it and jump back like "WTF?!!".

The tilt sensor works perfectly as well, as does the shock sensor when the bike gets a big enough shock, or someone keeps poking at it. I also liked how whenever the shock sensor warned away, it would alert the pager. The only other downside was it seemed to drain the battery pretty quick. Quick enough that I wouldn't leave it on overnight, after having it on all day. Hopefully they've improved that with the newer models.
On my FZ6, I've got a Scorpio I600. Much greater range on the pager. The shock sensor is nowhere near as touchy as the Gorilla, but it's enough to alert should someone actually be trying to steal or vandalize the moto. The tilt sensor also works perfectly. It also has the neat proximity sensor, which is also entertaining. It senses when someone is close(it's adjustable too), and gives 3 chirps to let people know they're too close. I love watching people scurry away after getting to close!

The Scorpio is very gentle on the battery, as advertised. It's also very small, and can easily be hidden away, and still function and be heard. Yes, it's much more expensive than the Gorilla, but for me it was worth it.
It's up to you to figure out which will work best for you, and of course how much you're willing to spend on it. You can always go with a disc lock as well, with or without an alarm. I like to layer my defenses, to make it as hard a target as possible.
Hope this helps! Feel free to ask me any other questions you may have on either alarm too! :thumbup: