On 13 Mar 2014, at 12:19, Daniel-Constantin Mierla <miconda@gmail.com> wrote:

On the other hand, there is no way to contact the device and tell to re-register.

This is a protocol issue, btw, not a Kamailio issue.

The SIP UA can subscribe to reg-info and get information about the current registrations for an AOR. If the server somehow deregisters a contact (reboot, expire, forced deletion) then the UA will discover it in the subscribe/notify events.