An intelligent interface provides a non-dedicated wireless communications path for reporting alarm events from a landline-based alarm system to a remote monitoring system. The intelligent interface includes a cradle for a cellular handset or other wireless device, and a network connector (such as an RJ31X jack) between an alarm system control panel and the PSTN. When a wireless device is present in the cradle, the intelligent interface bypasses the landline and routes all security calls from the alarm system control panel through an analog-to-digital digital signal processor and to the wireless device, which places a call to the remote monitoring center. When no wireless device is present, the intelligent interface allows the alarm system control panel to seize the landline to place the security call.