Please find at the below github an Anki 2 plugin that can be used to pull Kanji and Vocab that you have had in a lesson through the API into a deck. You will need your API Key, naturally.
@aina contributes here in this thread some better-looking templates. Thank you, aina !
It also now has a configuration dialog and a preferences file, so no more editing a python file to get the api key installed.
UPDATE 2014-01-26 slight update: use https to talk to wanikani.