The preview video (linked elsewhere) shows the ability to add an Extension to run a specific workflow using iOS Profiles. I'm pretty sure that functionality isn't present in the released version.
Can you not create a home screen link directly to the app?
<10 minutes of playing around with the workflowFEC418 url scheme>
Well darn, it looks like you can't. That's crummy. I thought I could get clever with `history.pushState`, but that doesn't let you change the URL scheme without a security error. It looks like this is the best way to do it on iOS.