A security system control panel or home automation control panel including an end-user replaceable cellular telephony module that is removable from the control panel without disassembling the control panel. The cellular module includes a body, a cellular telephony circuit coupled to the body, a cellular telephony antenna coupled to the body and the cellular telephony circuit, and a first connector coupled to the cellular telephony circuit and the body, wherein the first connector is sized and shaped or otherwise configured to be removably engaged by the end-user with a second connector in the control panel.