I've just released a new version of my Mongo driver for GObject. The main development this cycle was to support lazy connections to Mongo so that we could queue requests during network partitions, startup, and failover. As always, there is plenty of resiliency work to do, but the design is starting to take shape. The MongoConnection object will discover peers in your replica set from the seeded servers and failover upon losing PRIMARY status.
You can also use the mongodb:// URI connection strings now. It's not perfect yet, but the basics are there. (It uses GUri from the guri branch of GLib, which I really hope gets merged at some point).
This does support GObject Introspection, but it is not heavily tested.
Download mongo-glib-0.2.0.tar.gz. Source github.com/chergert/mongo-glib.
-- Christian Hergert 2012-06-29