The Moto360 has a pre-installed watchface that supports dual time zones (actually three; a main, analog time, and two side, digital time zones).
Facer seems to the de-facto watchface creator out there right now, at least while a formal API is released. The app itself is a paid app (a buck or two, I believe) but the watchfaces are free, and you can even make your own. This app, however, I'm not sure if it supports dual time zones (myabe it does, since it supports weather information and other extras).