-- Revised below 10/11/15 --
Until recently, I have assumed that when it came to installing a real life system I would base it on a Raspberry Pi. But then the Particle Photon came along. Three weeks ago I installed Particle Photon in my granddaughter's farm hoop house (they used to be called "green houses"). It is programmed to support 2 temperature sensors, 2 soil moisture sensors and it provides control of 2 switched devices: an electrified deer fence and a water valve for drip irrigation. Here's the smartphone web page image:
I originally intended to use a Raspberry Pi but the $19 Photon's simple web interface trumped the Pi's many advantages (especially the mature software development environment).
However, the Pi is not all together out of the picture: a Pi-based cron task checks on the Photon every few minutes and sends text messages if anything has gone wrong. It also accumulates statistics and provides a specialized weather report.
The Photon, sensors, switches and wiring cost under $70. My control program in C++ is about 80 lines long (originally, now expanded to 200 lines).
Does anyone know of a reliable motor setup for safely rolling the sides of the hoop house up and down (to control inside temperature)?
Revision: I've added more information on this setup (answering questions) at --