Just click three or more points on the map to measure the geodesic area defined by the points. You can drag the vertex markers and the area and perimeter will be updated. Click on the markers and confirm delete to remove the vertex, or type in new latitude and longitude values and select Save to update the vertex. The perimeter units of measure can be set to meters, kilometers or miles. The line color can be defined by the user. The calculations use the Javascript library from this
site. The measurements can be exported out as KML, WKT or CSV.