I'm currently building an exclusively internal web application for my employer, wherein there is a need to display information distributed across two browser windows (a scanned document and a data entry screen).
I've made a rudimentary test and it certainly seems to do the trick. Had I realised earlier just how simple chrome extensions were to make I would've used them all over the place.
You can specify window position with chrome.windows API. With appropriate
top values, windows can be placed on the second monitor.