http://code.google.com/p/libglim/source/browse/trunk/mdb.hpp The wrapper adds Boost Serialization, iterators and triggers to the mix. Any serializable class can be used as a key or a value. Triggers can be used to maintain indexes.
Notice that there is an MDB issue triggered when using this wrapper ( http://www.openldap.org/its/index.cgi?findid=7448 ), use at your own risk.