Webmention.io is definitely my plan for adding webmentions initially, and will probably be the step 3 article (IndieAuth is step 2 and being drafted right now).
If, or rather, when I look into writing a plugin to send webmentions I might bring receiving into it as well… but the more I look into Webmention.io, the more I think I’ll just keep things simple by having it continue to handle all of the receiving.
Thanks for adding the wiki page – I’ll be sure to add links and other information as I finish writing it up!