Probably not possible. Android Wear doesn't include the webkit
API, so it's unlikely that you'd be able to render your HTML content on the watch at all, which pretty well precludes using it as a watch face.
Given that, the only possibilities which occur to me are:
You might be able to use a third-party WebView
replacement, and build from that. The only one I know of is Crosswalk, and it's more about building a full app, so I don't know if it'd be possible to use in a watch face. There might be other options as well, but generally Google's WebView
works well enough that I doubt there are many full replacements.
You could render your WebView
on the handset, grab a Bitmap
of it, send that to the watch, and show it in a watch face. I can tell you from a experience that this is seriously nontrivial, and comes with some big caveats (like lag, battery use, and a connectivity requirement).
One caveat: it's pretty hard to definitively say anything is "not possible"; there may well be a way to do this that I'm not aware of.