XEP-0108: User Activity specific instances for general activities defined by users
XEP-0108: User Activity give a possibility to define specific instances for general activities by user using custom namespace as in example:
\<activity xmlns='http://jabber.org/protocol/activity'>
\<relaxing>
\<fishing xmlns='http://www.ilovefishing.info'/>
\</relaxing>
\</activity>
The ability for doing so in gajim (probably using some gajim namespace like "http://gajim.org/protocol/activity/custom" or similar) using GUI will be nice. Gajim already handle this custom status properly, if e.g. one set it by injecting code from xml console.