A concrete SPN-only use case

Seeking feedback:

proto.blandhand.net/patr/

The code is on github, but I don't feel like apologizing as much as I
probably should for how awful it is right now. I fear there may be some
interesting noise in this, wrt SPN (abandon or not), and testability in
general. As of recently, it works on iOS, which ... is a little trippy to
me.

Thanks,
-rb