This is actually something I have been thinking about a lot myself.
I am a huge fan of home automation, however I don't really feel comfortable using the existing home automation parts like thermostats, all sorts of sensors, smart lightswitches and so on.
This is because I am either not confident regarding the security of the wireless systems, or in the case of products from big brands (in which I would trust to an extent) simply the price-tag.
But for example at prices of 60+$ for a smart smoke detector (which is what I am currently thinking about), it would already make sense to buy an off-the-shelf smoke detector (15$?) and small form factor computer, like a Raspberry Pi or an Arduino, bring the two together and thus create one's own, more customizable and even cheaper smart home solution.
While researching on this idea, I discovered the Omega2 by Onion and it seems perfect for the idea. Instead of relying on third party, sometimes low level encrypted protocols, this device would enable one to use a full Linux computer with WiFi and even a simple Server-Client-system for the transmission using well known industry standard protocols and encryption for only 5$.
This device is only a suggestion however. If there are even better options, I would be thrilled to hear about them.
The automation principle would also apply to other machines one might have. from light switches, over thermostats to coffee machines, once the network would be set up it could be upgraded with relative ease, to include more appliances and even logic.
Thank you very much!