The current generation Holden Colorado (released in 2012) comes with a factory alarm system and is becoming quite a popular option for tradies.
The factory alarm which works with the Holden flip key covers the doors and the bonnet but has no internal movement sensor. The alarm uses the vehicles horn rather than a siren.
If the Holden remote key has a flat battery the alarm can be disarmed by placing the key in the ignition where it will recognise the transponder chip in the key.
The factory alarm lacks the option to protect your tools if you store them in the back.
I can add a PIR sensor to work with the factory alarm for $200.00, I can also add a reed switch to the alarm if you have a hard lid.
Upgrading the Alarm
If you wish to upgrade the factory alarm to give internal cabin protection and siren then I highly recommend the Cobra AK4615.
Below are some photos of how the Cobra looks in the Colorado:
Remote Engine Start Alarm
If you want to get really flash then consider a Viper Remote Start Alarm. It works really well in the Colorado.