@Morgan, it depends which SRID the geography data type is. "Methods on the geography data type that calculate an area or distance will return different results based on the SRID of the instance used in the method." msdn.microsoft.com/en-us/library/bb933808.aspx. For example, SRID 4326 (spatialreference.org/ref/epsg/wgs-84) will return distances in meters.

Also, I advise you looking for this question/answer on the main site, and if you don't find it, post a new question there; so other users can benefit from our GIS repository. Thanks.