Just curious if there is anything I should know about installing a remote start in a 12 matrix and what bypass i should get for this
Thx in advance
      Not a difficult car.  Assuming a North American "G" key vehicle.  There are basically two ways to do it.
1.  Use a full featured bypass module, like the EVO-ALL or iDatalink ADS AL-CA.
2.  Use a transponder bypass only module, like the PKALL or Key-OverRide-All.
There are many other bypass module options available.
Option 1 cuts down on the number of wire connections but requires obtaining a module flashed with the correct
firmware ( EVO-ALL = 79.03+, ADS AL-CA = TL5 ) and is slightly more expensive.  Option two requires a current 
release module, factory flashed with Ver 4.00 + firmware and more connections from the R/S syetm to the car.  Either 
way, you still have to make all the ignition harness connections.  
Your decision depends on the R/S system being used, your access to bypass modules ( and possibly the USB flash
cable ), and your skill / comfort level with soldering and Digital Multi Meter usage.
Here is a link to the current EVO-ALL install guide :  
https://fortin.ca/download/10711/evo-all_xb_(2011-2013)_camry_(2010-2011)_corolla(2010-2013)_matrix(2010-2014)_rav4(2010-2012)_-_gkey.rev-20130801.pdf
Here is a link to the current PKALL install guide :
https://www.xpresskit.com/DocumentDownload.aspx?documentid=6830&productid=196&firmwareid=1636
Please note that the PKALL guide only shows the necessary wires for the transponder bypass while the EVO-ALL
guide shows ( almost ) all necessary wires.  
While not exactly identical, here is a link to a similar install using an ADS AL-CA w/TL5 on a 2011 RAV4 with the "G" key :
https://www.the12volt.com/installbay/forum_posts.asp?tid=133996
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Soldering is fun!