Only if by "everyone" you mean people foolish and vapid enough to use Facebook and give them access to your phone.
[1] http://21stdigitalhome.blogspot.ca/2013/06/vcp200-voice-reco...
the downside was power usage. Motorola made one that was power efficient, used by nokia in the 90s and its pretty much the same chip in google's phone line today (just even more power efficient).
division is under lenovo now
Your phone reads sensor data as a base state.
It has a battery impact but much less than sending all the voice data continuously to a server somewhere. The biggest battery killer would be the wifi or 3G transmitting non-stop in that case.
Ad is easy. You don't have to understand context. Just listen for a thousand or so keywords related to products that are paying you. Then if detection happens apply some rudimentary sentiment analysis on the surrounding phrase and that's all you will ever need.
if you have a couple millions for me to start a small team we can offer this as a service next month or two.
Facebook has a lot of compute resources, but they wouldn't have to use it. Your smartphone is more than fast enough to do simple speech recognition. The accuracy rate wouldn't have to be that high - you won't get mad if you see an ad for a misheard keyword.