Q: Is there an alarm system I can purchase which I can seemlessly connect with my insteon system? 

A: There are several ways to integrate Insteon with an alarm system.

The most basic integration would be using an Insteon 2450 IOLinc which can accept a dry contact input and provide a dry contact (relay) output. Using this method one would typically connect a low voltage relay like the ELK-912 to the alarm PGM output or possibly the siren output if necessary and the relay output would connect to the IOLinc input. If a PGM output is used (eg. on a DSC Powerseries alarm), the PGM would be programmed to activate on alarm. A second relay and IOLinc could be connected to a second PGM if available to provide armed/disarmed status. Programming a PGM requires the installer code for the alarm system.

Another alarm option would be the Elk M1 Gold. By adding an M1XEP Ethernet expander, and an ISY994i series controller & PLM with the ISY plug-in for Elk (paid), complete integration can be achieved. In this case the ISY994 can be used as the main Insteon automation controller for events, schedules and Insteon programming. It can also 'see' all of the Elk M1 states such as zones status, armed state, alarm state - and rules can be triggered based on these states. The ISY994 with Elk software plug-in can also control the Elk system to arm, disarm and activate outputs for example, all based on rules or even control using an app.