[Kamailio-Users] get warning when sip client is not online

Hello, I have a kamailio setup running for several SIP devices. I would like to be warned whenever one of those devices is not reacheable anymore. That means when they go offline or are not anymore registered to the kamailio server. (timeout, unregister, ...). I am using the location table so we would be able to write a script that just at specific times checks the difference between the subscriber table and the location table but maybe there is a much better and more realtime solution. So basically the question is : how to execute a script whenever a host gets removed fom the location table. I am running Kamailio 3.0.1 All hints are very much appreciated :)