We are finally ready to ditch our land line, and I am considering transferring that number to my cell account and using an HAI C3 device for the few landline calls we get and for monitoring the Elk. Any comments, opinions, suggestions or alternatives re: this device? Our cell reception is so-so here with iPhones unless near a window, but I understand the C3 has a high gain antenna. Also - I am considering mounting it in the attic and can't find temp specs for it - thoughts and info re: that appreciated as well. Thanks in advance. Joe