agame wrote:I've done similar and swapped proprietary hardwired alarm systems for DSC panels interfaced to Indigo.
The DSC plugin, coupled the Envisalink board added to the DSC panel, works well and is completely stable. It exposes all the device states, and provides access to the usual end-user controls including arming & disarming. One limitation is that the DSC can't see other sensors you might add natively to indigo over time...however wiring one of the relay outputs on your DSC board [controllable by Indigo] to a spare input, its also possible to create a 'virtual' sensor .... for instance, enabling the alarm to respond to z-wave door sensor being tripped.
Its debatable whether a 'traditional' alarm system is really necessary...but there might be stability, usability, or insurance-related arguments in favour. If its just using the sensor inputs, various other I/O options like that described above are worth considering.
I agree the DSC/Indigo combination is excellent, for me having a dedicated alarm panel that functions independently of Indigo but is seamlessly integrated is the way to go. Same approach for heating with Evohome. I also like the fact that the envisalink provides monitoring and alerting separate to Indigo, for example when the "phone home" heartbeat drops with a lost connection you will be notified.
From a DIY perspective the DSC is a little daunting, but lots of solid online information both on hear and in the wider security forums. Once you get your head around the setup it is not too bad, and even a few people on here are pretty knowledgeable (I would pitch in to help).
In my setup I re-used the existing PIR room sensors, entry door switch and panel wiring. I purchased the DSC touch screen panel that looks pretty cool but is not cheap with a wired traditional keypad for the upstairs in the master bedroom. You would also need the interface board (in my case the envisalink) to connect to indigo. Bear in mind the envisalink needs an ethernet connection, but you can connect it to the key bus of the alarm (used for the keypads and any expansion modules) so depending on the wiring you may be able to place it near an existing network port. In my case an spare cable ran to the loftspace and I was able to connect the keypad and envisalink to that as well as a zone expander.
Envisalink comes with an APP and you can arm, disarm etc with that as well as check zone status, logs and with notifications. You can also do pretty much all of that within Indigo, we certainly arm via the Alexa plugin and extensively use triggers from the PIR sensors.