What about setting "application_name" for connections to PostgreSQL based database backends?
See: http://www.postgresql.org/docs/9.3/static/runtime-config-logging.html#GUC-APPLICATION-NAME

This might allow better differentiation between sessions from frontend, server, users, ...
Especially when there is one database user for any component, what probably is the case for most installations due to lack of ZBX-7604

Any Zabbix component should have a dedicated "application_name" possibly honoring the optional "Installation name" ( https://www.zabbix.com/documentation/2.2/manual/installation#step_4 )

Of course this would be valuable for any database backend that support this kind of functionality.