Yeah, we discussed this a while back.
There was some other project doing binary attestations too, but I can't recall it.
At its core, an Attestation Event is a simple valid/invalid on the referenced assertion event (e.g. an app release).
Zapstore and others could interpret this as a simple vouch.
Another way is to actually publish some kind of specific app vouch event with more detail in it that some expert can publish (perhaps even zapstore) that other experts can attest to.
I think the later is more robust, the former simpler though. Both can be used in parallel I guess.
