Tying the bits together is always the hard part.
I've looked into a lot of this over the years. My observation is that there are great industrial solutions if cost is not an issue and you have an engineer on hand. However, there isn't much our there in the gap between industrial systems on the high end and discrete single-purpose controls on the low end. In a lot of cases, simple monitoring is enough, and BBQ thermometers or cheap dataloggers are a good solution.
If you want to control things, though, I start to worry about end-to-end system reliability. What needs to be working in order to have adequate safety?
Being an aerospace guy, I like things that are self-contained, simple, hard-wired, and fail-safe. Depending on Internet access or on a computer with moving parts is a non-starter for me, and I'm suspicious of wireless for mission-critical control functions.
I'd also like to be able to use any sensor or control device out there. Unfortunately, almost everything uses proprietary or at least undocumented protocols. Ever try to get an actual schematic of even a simple Taco zone controller?
For another example, the MFi hardware is nice, but we've never found an actual description of the signals / protocol between their sensors and their port. Proprietary, as far as I can tell.
After a lot of hassle, we got an agreement with Insteon to support their devices, but their documentation is almost non-existent.
Our best result so far has been Monnit - they have a wide range of 900mHz wireless sensors, and we are able to integrate all of them. Not as cheap as MFi, though.
We made the decision to go open-source with our system, and a good many people (some of them on this forum) have built their own versions. I feel like that's the right approach, and it's allowed users to add their own hardware and software. We've recently added the Beaglebone and Raspberry Pi to the list of supported CPU platforms, and we have people adding their own software to do cloud-based data mining across multiple systems.
Unfortunately, we can't match the mass-produced made-in-China prices.....