Hi Claudius,
First, there is a very basic responder functionality currently implemented, the 'env.prompts' setting:
If I had to guess, I'd guess it's too simple for a "fully automatic" interaction with a serial console, but it's worth trying if you haven't already.
Second, stronger expect-like behavior is on the roadmap; version 2 (alpha out very soon!) is built on the Invoke library, which has its own "2.0" rewrite of the above feature, as 'watchers':
I haven't needed anything more complex yet than the sudo-oriented FailingResponder yet, but as you can see from the generic StreamWatcher class, the intent is to allow for pretty much any "examine output streams, yield responses" use case (and for users to write their own instead of being limited to what's in core; though of course any generally useful patches are likely to be accepted.)
The specifics may yet change (e.g. attempting to submit deltas of the output streams instead of the full captured text) but the overall concept of stateful per-thread watcher instances seems likely to stick.
Best,
Jeff