Possible to use Siri to trigger custom actions?
That’s one interesting idea. It seems to be possible by registering custom vocabulary in your app. Since there is SiriKit it should be possible. Besides people from Homebridge achieved the same you want with garage doors and so on.
https://github.com/nfarina/homebridge/blob/master/README.md

Things like custom vocabulary can be found here:
https://developer.apple.com/documentation/sirikit/registering_custom_vocabulary_with_sirikit

So if I understand the docs correctly you can specify 

IntentPhrases that allow you to react for a word shell for exemple

But I love the idea. First thing I will connect will be ‘fastlane’ and I will shout ‘deploy!’