This is one of the great aspects of Ignition. I have built a building automation suite with it.
I have struggled through many parts of it incorporating features and technology I had very little experience with.
I did not have the option to spec any hardware which has made my struggle even greater.
They key is to find the matching protocols. Examples:
For energy monitoring I use Eaton power expert current meters over mod us tcp
Hvac controls use Nova logic one controller and watt master controls. To support this I incorporate the active x controls to view a web server on the Novar and also use scripting to parse the data into tags.
To support watt master which is proprietary I incorporate a dependency to a pre installed application on the client
machine by externally launching an exe. Not the best but it was a solution.
For lighting controls I incorporated a soap/XML server from cutler hammer that uses a proprietary mod us map
I send XML formatted messages to turn breakers on and off. These are dedicated to lighting.
I can keep going more but I’m using a tablet I will update later with more of the architecture.
The moral is that with ignition and some creative connectivity all of these things are possible.