Well the Vivofit step tracker will connect to an HRM strap for calories calculation and can also be set to detect and turn any activity over 15' to a "running activity".
But i'm not using that, I have a Garmin Forerunner 220 for tracking the runs.
In any case, you end up in Garmin's platform with "Total Calories" which are split in BMR and "Active Calories". Active Calories are also split between walking and running (or if you have other activities like cycling).
Does their API expose any of this? I think it should, because Garmin has integration with MFP and you can get a "calorie adjustment" in MFP from Garmin activities (walk or run or whatever).
I suppose I can wait for your MFP integration as well, but I'm sure there are people there that might be interested in getting more data from Garmin as well.