[balladeer]

I think the better option would be APIs for desktop app(s), maybe with a stock basic functionality desktop app. Definitely not an "offline" app based on a particular web browser.

As a Firefox user I already dislike Gmail Inbox and WhatsApp (web) being Chrome only. The former has said "Chrome only for now" for quite long already.

[drvortex]

It is actually a shame that it is based on PHP. If it was based on pure JS, there was hope to make a desktop version easily using node-webkit or something.