The most common way to get a free wireless alarm system for your house is to sign up for a one, two or three year home security service contract with the company of your choice. Often the installation and equipment are provided free of charge with a long enough service contract.
Essentially, the company is banking on making money off of you for several years to come, and on that basis, they are willing to provide the equipment and installation free of charge. You can also browse to https://buffalosecurity.com.au/service/alarms/ to get more information about the security alarm system.
The monthly service fees mentioned in all of these options cover the actual home security service that you get from having the alarm system in your home. The alarm system itself is not enough.
You must get a service provider that will respond when your alarm goes off by contacting you to ensure there is or is not a problem, and contacting the necessary authorities for you when there is a problem or you cannot be reached. This ensures full protection of your home from both theft and fire.
Since you need this monthly service anyway, it makes sense to sign a lengthy contract to get the free system and free installation. After all, it makes no sense to sign a three-year contract if you plan on moving in two years. However, outside that unlikely scenario, it makes good financial and logical sense to go ahead and sign that contract to get the free system.