The system hasn't yet been fixed in location but seems to work as advertised. Its major drawback, as far as I'm concerned, is that it only works via mobile phone. I have a couple of them, usually switched off and only used for rare, essential communication. I had hoped to control the system via an Android tablet but it is not 'recognised'. Can anyone confirm that these devices require comminication via a 'telephone' (as distinct from internet) connection? ... the tablet is just a 10" Nexus.