We moved in to a house where previous owners had ADT's alarm system. The board is still there and I'm planning to remove it because it doesn't do anything at the moment.
But the (wireless) sensors are still on doors and windows and as far as I can tell are still functional. I would like to reuse those, but I would like a 'local' alarm system (that would just trigger a sound but nothing else), as opposed to centrally monitored one that you have to have subscription for.
The question is what are (affordable) options for units that could connect to existing ADT's sensors and that are reliable enough to cover basic security situations? (I don't care about sophisticated attacks. I just want to know immediately if anyone breaks into the house while I'm there. Everything else, I don't worry about.)