I recently got ahold of Panasonic's newest field monitor, the 9", 720p-resolution BT-LH910. I'll be reviewing it shortly, but can say I was very impressed with its size/weight/picture quality. It's about as big as you can get while staying in the "field monitor" category, and is very sharp. And it's big enough, in my opinion, to work as a studio monitor.
You can read its specs here on Panasonic's site.
It's pictured next to my trusty BT-LH80 (7.9" monitor), using some test footage I shot last fall of a Civil War re-enactment in California (a rare thing in these parts, unfortunately!).