The Jabber SDK should in general support any device controllable via CUCM CTI (TAPI/JTAPI). Per the supported device list here, CTI supports Extend and Connect devices, so we would expect this to work with Jabber SDK: https://developer.cisco.com/site/jtapi/documents/cti-tapi-jtapi-supported-device-matrix/
That being said, I have not tried this myself or heard of anyone using it, and it's possibly not a configuration directly tested by the Jabber SDK team. Would suggest testing thoroughly...let us know if you run into any issues.
Thank you very much for your answer!
Allow me to re-phrase the question: does the Jabber SDK have an API call to do call forwarding to a certain number?
If just simply setting a call-forwarding option (like Call Forward All) destination, then no: the Jabber Voice/Video SDK does not expose a way to set call forwarding.
You will want to look at the User Data Services (UDS) API for that:
See the /extension resource:
(I've noticed that the XSD schema .zip file on DevNet does not include all of the schemas - namely only the 'public' resources are present. We will be updating this shortly...meanwhile you can do a GET on /extension with an existing device (i.e. with forwarding set) to see the XML needed when you do the PUT to perform an update)