I’d like to add my support for a “real” binding, as with Version 1.3 of the Nuki Bridge API there’s also the above callback present. This feature of the Nuki Bridge triggers in every event of the Nuki Smartlock. With this there’s also a update on the respective openHAB items, if the Smartlock changes the state manually or via a smartphone App. Of Course you could fire regularly with the API to see, if there are some changes, but this drains the battery pretty fast.
See https://nuki.io/wp-content/uploads/2016/04/Bridge-API-v1.3.pdf for Details. /callback is the action, where you could add up to three endpoints which will be notified (via JSON) with updates.
@ben_jones12 did a workaround via a python/bottle described here: Receiving `Content-Type=application/json` payload on REST API but I’m afraid, I’m not so deep into WSGI, that I’d like to open that bottle (HARHAR). 