Always glad to see more things happening in this space, but most devs already BYOIDE and would probably just like better integration with their existing tools:
So there are three layers of compatibility we expect to see with external IDEs:
0) No integration - Open a WebIDE window with editing turned off and use it (or command line tools that drive it) to manage device connections/pushing/etc. 1) Simple integration - Most of the basic device connection management will be available through command line tools, it should be incredibly easy to drive that through editor/IDE configuration. 2) The whole nine yards: Speak a remote debugging protocol and get full control over the debuggee.
As far as the whole nine yards, you can either use remotedebug's protocol and proxies (although development seems to have trailed off there?), speak each browser's protocol natively, or maybe down the road the protocol abstraction we're working on at Mozilla.