I use a SpeechMatic Travel Mike (from KnowBrainer). Very accurate, and you can dictate from a reasonable distance from the mike with little loss of accuracy.
Interestingly, the version 13 (not available in medical as far as I know) is by far the most accurate, and even will work pretty well with the built-in microphones on laptops.
Best mikes are in cellphones. No idea why they can't be made into standalone mikes -- but with Dragon you can use your smart phone as an input device. Works ok if you have a good WLAN, but somewhat touchy.
