This apparently has been requested before (several years ago), but I'm shocked that more organizations aren't asking for this feature.  We recently migrated from eTapestry to RE.  We regularly use radius searches to identify constituents in specific areas around the country for targeted emails and invitations.  This was simple in eTapestry, but the work-arounds in RE are cumbersome (or expensive).  It would be nice if this functionality was built into the design of the product.