I have ordered 3 of the Ecolink Door/Window sensors from here, and they are currently on sale for around 25 dollars a piece.
They are Z-wave and on the ‘approved’ list of things that play nicely with ST hubs. They ALSO have a header
inside the unit where you can use hardwired reed switches found on wired home alarm systems. You can create different ‘zones’ such as multiple windows, and seperate door zones etc. if you like. You can use any of the prewired reed switches already hidden in your door and window frames (during home construction typically)…
This setup is easier for a ‘dead’ alarm system, or one that is not completely setup from the original installer. Mine is a Honeywell/Brinks system.
This video shows the connector headers that I am speaking of.
Hope this helps guys!