Cheap device to connect my magnet switches to openhab

Hardware Home Automation
1

Hello,

Im looking for cheap devices to connect my magnetic window and door sensors to openhab. My first idea was to use ESP8266 in combination with MQTT.
Power supply is taken from the KNX bus because KNX bus is on all positions.

Any other ideas?

2

Nope, great idea if you have a decent stable power supply

3

I use the zwave Linear WADWAZ1 for a number of applications like this. They have some terminal posts that you can hook up switches to, so pressure sensitive mats, water sensor, door sensor (in addition to the included one), etc. There are several rebranded versions of this device (Monoprice, Vision, Zipato, etc.).