I installed the Model 7017 Gorilla Alarm with Pager on my GTS. $179.00 from Scooter Works in Chicago.
It really works great but the tilt sensor is really intended for bikes that have side kick stands. The tilt sensor is a single mercury switch that is intended to be normally open when the bike is leaning on the kick stand.
I made my own tilt switch with two mercury switches mounted belly button to belly button and glued on a small piece of MDF board and angled away from each other. Now my scoot can be on the center kick stand and any movement leaning the scoot left or right (about + or - 20 deg's sets off the alarm.
There are two other sensors on the Gorilla alarm. One senses shock and the other senses any voltage change on the electrical system. Prevents from hot wiring the scoot.
The shock sensor is very sensitive. So sensitive that the mercury tilt switch sensor may not be needed. However, you can adjust the shock sensitivity with the remote pager to a lower level thus not causing the alarm to go off in a thunderstorm or loud traffic or concerts.
The electrical sensor works well too. With the alarm on, just inserting the key and turning the ignition on sets off the alarm. You have to be very careful putting the key in or the shock sensor will set off the alarm with just slight bumping of the key in the ignition switch.
The range on the pager is only about 1/8 mile with the scoot in the garage with the door down. I will range test it when it warms up some around here. (Pittsburgh, PA)
I have also installed a headlight and tail light modulator and a cigar lighter and a 3 button garage door opener.
Everything is working well.
The GTS250ie is out of sight. I have owned scoots for over 40 years... this thing is a rocket!
The GTS is no doubt the highest performance scoot I have ever owned.