OK OpenHAB is a confusing at heck setup for running a home IoT (Internet of Things) network. But, its free and its very flexible. This article goes over how to make some cheap sensors for your setup with arduinos, and using NRF24L01 (basically wireless transceivers). Apparently alot of this stuff comes from mysensors.org too. Either way, this maybe worth looking into (oh everything is transmitted with MQTT, another thing on my list of stuff to look at).
http://www.makeuseof.com/tag/diy-smart-home-sensors-arduino-mysensors-openhab/