I have some polygons which can be anywhere in the world. I would like to compute their areas.

The GeoDjango docs for GEOSGeometry.area don't specify whether it is geometric or geodesic area, but given that GEOSGeometry.distance() says that "GEOS does not perform a spherical calculation even if the SRID specifies a geographic coordinate system", I suspect that it is a simple geometric area.

I'm willing to write a little code, but the shorter the better, of course.

We do have a working geodesic distance function already.