Looking for an API trigger via journey

Looking for an API trigger via journey

It's great that SMS and email are already integrated but I am really hoping you add the ability to fire an API or trigger a custom function like in CRM. I am hoping to be able to incorporate some other marketing channels into my journey such as physical mail (via lob.com) and voice broadcast (via slybroadcast.com) which could both simply be triggered if I was able to create an API request in the journey builder. That would be awesome!