I’m only slightly involved with this effort, but I’d be disappointed if we couldn’t get multiple monitors to work. That’s a pretty interesting use case. Higher up in the stack, the webengine_kiosk package lets you start two browsers up so that you can have one running fullscreen on each monitor.
Debugging seems a little slow at the moment due to work priorities and a few cryptic errors. I’m optimistic that we’ll get there. If you’re interested in collaborating, it looks like most discussion has been in the #nerves channel on the elixir-lang slack recently and issues/PRs to those projects.