Force PostgreSQL clients to use SSL on Amazon RDS
Looks like this has finally been added. From the docs:


  You can use the rds.force_ssl parameter to force connections to your PostgreSQL database to use SSL. The default value is 0 (off). When you set this parameter to 1 (on) and restart your instance, your database will refuse any non-SSL connections. This parameter also sets the PostgreSQL parameter ssl to on as well as modifies your instance's pg_hba.conf to support this SSL configuration.