Thank you for your interest.
I have added some docs about Data binding relay.
Concerning the state machine extensions, it's not possible to have properties passed along with state change.
We wanted to add this feature at first, but we decided that it was better to retrieve data from a model rather than from parameters. The reason is that this kind of data is very volatile, and several times we had situations where a transition from one state to another was asynchronous. For instance, validating user action on server side was often needed and therefore we wanted to avoid passing data all over the place, especially when you want to bring decoupling.
One idea we had though is that state names could be holding some properties (for instance a user id). Sort of what you do with URL routes on server side, you could match some part of the state string and extract info. That would be a great feature to add.