Does anyone know whether or not the Ademco Honeywell wireless door/window sensors work with Smartthings? I am looking to cancel ADT and would love to be able to use my existing window and door sensors.
Generally speaking, no. Alarm panel sensors use proprietary radio protocol and cannot communicate with ST. Depending on the type of your alarm panel, you may be able to link your alarm panel with ST and use it for self-monitoring though.
@IanWedlock If you are using an ADT Smartwatch 3000 (more commonly known as a Honeywell/Ademco Vista 20p) you can definitely use the entire security system in conjunction with SmartThings. Please see the thread here: ADT Smartwatch Pro 3000EN Integration
Main post with instructions is here: DSC/Vista Alarm Smartapp and devices based on AlarmServer
It requires running software called AlarmServer, so you will need a spare computer and an Envisalink 3 module to get the alarm panel on your network. Good luck!