/subscribing as I am interested in your project. I want to build something similar when I have some time, but with a PCDuino instead of a Pi - purely cause I have a PCDuino and not a Rasberry Pi. As my "sensor hub" I'm planning on using an Arduino Leonardo (again, what I have at hand) or perhaps even a "bare bones arduino". For communications I might be looking at using I2C, or perhaps purchase a couple of 433Mhhz radios - they're much cheaper than bluetooth / wifi.