I just wanted to share this because I'm not sure if anybody was wanting something like this but me. I wanted an alarm system that ties into the stock keyless system so I don't have to carry around a separate remote and have to deal with an endless amount of wiring and going through alarm/audio shops.
Basically I searched and search and stumbled upon this post:
http://www.ft86club.com/forums/showthread.php?t=52937
It was exactly what I was looking for so I bit the bullet. I contacted the vendor and the international sales manager was such a great help and a breeze to deal with. I ended up with the Vision 1480B along with a few extras to help shorten my install to less than an hour. Most of the time it was just snaking 2 wires through the firewall and wire management(aka zip-tying). You can get this programmed from the vendor to work with both the normal keyfob Premium model or the keyless Limited model BRZ/FRS. This also as the option to enable auto-lock, so the doors will automatically lock if you go over a certain speed (22 mph i think?) and unlock once you go into P or use the parking brake.
Here's a short picture blog of my install:

The box.

Double-sided taped it to the side of that controller box underneath the left inside behind the steering column.

Connected to the OBDII using a splitter which relocates the stock harness.

This is the programming switch which also acts as the alarm/error indicator.

The only wires required to be routed through the firewall and spliced/soldered to the alarm harness for the siren.

The siren with a bracket designed to be installed to any existing 10mm bolt. In this case, it was being used but I managed to squeeze it in with plenty of clearance from the hood. (Ignore the temp sensor just chillin' there, it's a work-in-progress :P)
There's an adjustable shock sensor but I don't have a picture because it's glued to the plastic tray right near the bottom of the dimmer switch and I didn't want to disassemble it for a picture.
Here's the link for the manual if you want to have a more closer look at the installation and features.
http://visionsecurity.jp/en/systems/...ion_Manual.pdf
It was a pretty penny to pay I might say but for a peace of mind plus the ability to retain stock keyfob, I consider it well worth it.