I'm currently working on providing external keyring functionality to Pidgin IM and was thinking of adding a support for storing passwords in KeePass.
For all supported keyrings (KWallet, GNOME Keyring, libsecret) and these not yet supported (Windows Password Store) there was only a need to connect to some daemon and ask for password. I don't see such information, how to connect to KeePass - is it at all possible without writing a plugin for KeePass?
I wanted to support this password storage out-of-the-box, without need for installing any additional software.
KeePass V1 has external hooks, off by default. V2 requires a plug-in.
You can use the KPscript plug-in to do basic things without writing a plug-in.
There exist various plugins for IPC, e.g. KeePassHttp (which is used by PassIFox and ChromeIPass; see https://github.com/pfn/keepasshttp), KeePassRest (http://keepass.info/plugins.html#keepassrest), and others; you might want to have a look at the plugins page (http://keepass.info/plugins.html).