One small - but still useful - thing is the first public beta release of the kdev-sql plugin. It allows you to execute SQL queries from within KDevelop. Simply press Ctrl+E (or Run->Execute SQL) to execute the contents of the current file as SQL query.
The only use case this is trying to solve is debugging and performance testing of queries.
Database connections can be configured per project - all QtSql divers are supported.
Get the script here: kdev-sql-1.3.80.tar.
(compatible with KDevelop 4.4)
In future other features like schema browsing and autocompletion could be implemented...