According to a post on Peter Beverloo's blog, "The webkit prefix has been dropped from the Vibration API implementation as it reached Candidate Recommendation."
In Firefox, the Vibration API can be found at navigator.vibrate (per the spec), not so in Chrome 23 - with or without the webkit prefix. I've tried enabling experimental javascript in chrome://flags but to no effect.
Despite playing around in devtools and plenty of searching on the net, I'm still unable to locate this API. Where is it hiding?