This is great if you are using an old SIM that still operates using IMSI on the sNode B Tower, its also bad because this is simply another overlay band-aid fix which bloats and slows your phone down, the privacy phones made by Obsidian Intelligence Group (obsidianintel.com) don't have this problem and they are also impervious to the SS7 network, I would check them out.. You can find more info on their twitter page @Obsidian_Intel as well.. I picked one up a few weeks ago and it is fantastic I couldn't be happier with it.