Stuff has gotten more sophisticated (a sufficiently new enough iPhone can do background sound recognition for things like smoke alarms, barking dogs, etc to help deaf users - I think it uses significantly more battery, however), but there is no way in hell Apple and Google are letting others program or control this functionality.
I have said this over and over and over to friends and in online discussions: constant voice recognition or even just voice recording and transmitting would leave a huge footprint in terms of battery use, generated heat, data usage, and in the apps themselves (code and API calls). This stuff would leap off the page for any security researcher and be front-page mainstream media news.
And lastly, I point out that these companies do not do constant voice recognition...because they do not have to. Social media buttons, third party font services and javascript toolkits all feed Google and Facebook data about what pages you visit, at least from your IP even if you're not logged in. Google Maps alone constantly gorges itself on location and passively gathered bluetooth/wifi data, for example. Google sees the plain-text of any alert sent through Google Cloud Messenger, unless the app merely uses GCM to poke their app to retrieve the actual notification via their own servers, but google still knows something happened involving you and WaterBNB, or Fleabay, or Shminder Dating, etc. Your device's presence on a particular network and its activity level from your usage tells them even more, and they can know a lot about what you're doing because all the "good stuff" in Android isn't in Android, it's in Google Play Services, or whatever they call it these days. Then there's all the mobile app analytics data companies.
One of the reasons I switched to a used iPhone was because the privacy preferences allow you to switch off a huge number of 'system' data collection stuff that Android doesn't. It does wonders for one's battery life when your phone isn't constantly collecting wifi/bluetooth/cellular/GPS data for location mapping databases, noting when you go into stores, collecting traffic data, etc. This year I (accidentally, thanks to a not fully seated cigarette power adapter) managed a 6 hour trip w/ Apple Maps navigation, and it only used up about half of my battery. I was stunned.
> For your smartphone to actually pay attention and record your conversation, there needs to be a trigger, such as when you say “hey Siri” or “okay Google.” In the absence of these triggers, any data you provide is only processed within your own phone. This might not seem a cause for alarm, but any third party applications you have on your phone—like Facebook for example—still have access to this “non-triggered” data. And whether or not they use this data is really up to them.
> “From time to time, snippets of audio do go back to [other apps like Facebook’s] servers but there’s no official understanding what the triggers for that are,” explains Peter. “Whether it’s timing or location-based or usage of certain functions, [apps] are certainly pulling those microphone permissions and using those periodically. All the internals of the applications send this data in encrypted form, so it’s very difficult to define the exact trigger.”
Now, I don’t know much about Android, but I do know how it works on iOS: the “Hey Siri” trigger is run by a specialized “always on” coprocessor that is designed to only detect the trigger word, and when it does it will power on the rest of the device to continue responding to the request. Until that happens your phone is pretty much entirely off: the AP isn’t powered. You can’t just “add a trigger” to listen to.
Plus, even if apps could somehow add triggers, or abuse background execution to do their own detection, you’d be able to see it. Bluntly: if you’re actually a “senior security consultant”, you need to do better than throw up your arms and go “boo hoo it’s encrypted who knows what is going on”. Reverse engineer the apps and find it…