I've been using my Nokia Lumia 920 extensively now and wanted to add a camera for those longer shots where anything not close or midrange all but disappears on the 920's tiny fixed lens. The Panasonic Lumix four-thirds cameras seem to offer the best capability in a tiny and easy to whip-out package that is in a similar use-case as a smartphone. Albeit, with the ability to change lenses and use a longer lens.
Budget could be as much as $1000 AUD if the camera was really going to give a lot of capability and ease of use, etc. Otherwise, looking to spend around $600-$700 on a body and one excellent lens for those situations where the 920 just doesn't cut it (longer midrange and landscape).
The other option I have is to buy a couple of good lenses for my D200. But, that camera isn't going to be something I carry around with me all the time like I do with my smartphone and could do with a four-thirds. I'll be travelling for the next six months (at least) and would prefer to capture opportunities as they can present themselves at any time.