I have a question that potentially spans the charters of several different SE sites, but I'm hopeful there's still a "best" site to ask. My question concerns a small one-of-a-kind home automation project that I will be coding, building, and deploying in my own home. Despite the small size of the project (think: weeks of work and no more than some small hundreds of US$ in total hardware costs), the scope of the question is broad: I know how to build it, but I don't know how to build it cost effectively.
I will be doing all of the actual design, coding, and and physical assembly/soldering work as needed, so my chief (only, really) question is minimizing the hardware costs. I have expertise in all of the skills I'm likely to need, except sourcing cheap hardware.
A very rough draft of the question follows below the rule. I'm including it here to help you redirect me to the best SE site, as asked above. I'll flesh it out a bit more before posting (hopefully with some of your own kind feedback) once I know who the question's audience will be.
My project will see a single deployment of a 2 or 3 physically separate but networked stationary hardware panels each with a small LCD screen (16x2 backlit mono character array would be about the bare minimum), 2-4 hardware push buttons (or touch screen if that's cheaper by some miracle), sound for use as an attention getter (so it could be anything from a simple buzzer, to a small computer speaker). The custom software they'd run would have 2-way communication to a headless DMBS server (no need to buy additional hardware for that, I have plenty of servers I can run the backend software on).
My initial thought for the hardware was to use a Raspberry Pi plus a USB Wi-Fi dongle, 16x2 LCD and a couple of buttons wired to GPIO, but even that seemingly simple solution will run me in the hundreds for 3 units. It's still the best option I've come up with so far. A general purpose computer like the Pi would certainly get the job done, but it's overkill, I'm still hoping there is a cheaper elegant solution since my I/O is a couple buttons and 2 lines of text.
Deploying as a mobile app is an option, but in my current situation, I am not always within range of my mobile devices. Fixed installations are ideal, here. Used previous-gen mobile phones or iPod Touches stuck to the wall might do.
Of course to fit the requirements of posting on the SE network, my question needs to have an answer (not just opinions or options), so I suppose I would frame it along the lines of the cheapest readily available hardware that meets the requirements I've specified.
Where would I ask a question like this? And how could I revise it to attract better quality answers acceptable by the community?