Continuity Sensor

Are there any sensors that detect continuity for existing non-smart devices? I have an alarm system that has a NO/NC output. It’s only rated for 28v, so I can think of a few ways using smart switches to integrate this, but I’d have to find a low voltage switch. Ideally I’d rather just have a continuity sensor though if one was available.

Any door contact sensor could be used here, many have terminals for external contact inputs.

This one from Monoprice has connections for an external switch could work -

I’ve used this one to create a custom button and it works great.

Great suggestions. The window/door sensors have built in leads and should work just great!