Very good observations.
There are expensive “custom” (through authorized dealers only) home automation systems that are “always listening and built-in”; these require quite a level of sophistication to be able to avoid false triggers …
I just purchased a Moto X phone which uses “always listening” technology; but it is tuned only to one specific person’s voice. That, along with reasonable proximity, seems to avoid false triggering, though I have not tested extensively.
Somehow, I have trouble believing that avoiding false-triggers is an insurmountable challenge, particularly if we are willing to accept unusual trigger phrases (e.g., instead of “OK Google Now”, or “Hey Computer”, why not “Open Sesame Do This” … – in practise, linguistic databases could be extensively searched for sound patterns that are unlikely to occur from television broadcasts or normal conversation or noise).
I am a Beta Tester of The Ubi (http://www.theubi.com) and my primary issue at the moment is false triggers; but I also am aware that this is a high-priority focus of the developers. Then again, I wish they could afford to license Google Now and/or Moto X’s various sound processing and voice phrase handling technologies.
And… then partner with major HA systems, such as SmartThings.
Lots of opportunity here for those willing to invest in the challenge. At the moment, this research is costly and results in expensive end-products (if any).