Thanks Tangent! I'll research those options a bit further.
I forgot to mention i had ADT did out house from like 20 years ago and we still have their keypad...i wonder If i can just reuse their wires and sensors...everything needs new battery though by now. Lots to learn about alarms.
That makes a difference, you should be able to reuse what they did. Door and window sensors are really simple, they are just a switch that opens or closes when a magnet is close to it. So the switch is installed in one part of the window, magnet on the other part, and when you open the window either the switch or magnet moves, and the switch changes state, and alarm goes off.
As long as all the switches and magnets are still there, with wiring, they will work. And you can replace any that fell off or got lost over the years.
In the long run, wired sensors are preferred, you don't have to worry about changing batteries and such.
Is the panel still working? Do you know what kind it is? My ADT panel is pretty old, and still works fine. And one of these days I'm going to get a Eyez-On Envisalink EVL-4 to connect to it so I can remotely monitor and control it. My ADT system is a really a Honeywell panel. You can get the part number if you look inside.
BTW, batteries are pretty easy to change, they just use 12V SLA batteries that are readily available.