I was curious since the audio may be different than a standard smoke/fire detector, if the (ECFF319) will work with the alarm for both carbon monoxide and smoke alarm sounds that the Nest Protect produces.
The ECFF319 is generally not for use with dual-function devices. It is an audio detection device and listens for the standard audio cadence of a smoke detector.
If the smoke detector audible alarm is different than standard wired smoke detectors, it would likely not function appropriately.
If I can use it, how close does it need to be?
If using an ECFF319, it needs to be installed within 6 inches of one of the interconnected smoke detectors. If they are truly interconnected and all sound when one does, only one ECFF319 is needed. The ECFF319 is generally intended for use with code stipulated 120VAC wired smokes.
I really wish ADC would fully integrate with all Nest products.
We are always happy to forward requests to Alarm.com! As far as the Protect goes, alarm signals generating a possible authority response must come from the Alarm.com compatible alarm panel. I do not expect that to change in the immediate future, but I cannot say with 100% certainty of course.
Integration with other automation products though is added routinely, and as more and more people want integration with third party products, more will be brought under the ADC umbrella undoubtedly. I cannot say whether video will adopt third party products, since as of yet they have mostly opted for controlled in-house products. Skybell HD is the first third party integration with video. Recently there has been talk of cameras which seem to move away from traditional surveillance though, like a table-top wide angle with two way audio.