The closest analog would be the Android camera, and it asks if you want to turn on autoupload or whatever. And it doesn't upload at all if the camera is being used by an app, even if you have that turned on, which would be the same case if people build apps to use this device.
I disagree. The closest analog is the Google location services, which continuously uploads data about your position and local wifi networks to Google, and is not very transparent about what it's doing: http://www.pcmag.com/article2/0,2817,2384751,00.asp
It's far more likely (if this catches on) that this will just be another sensor in your phone that apps can use, and if Google wants to improve maps or whatever, they'll just ask people to "contribute" scans, like they've gotten people to basically make street view for them[1].
[1] http://www.google.com/maps/about/contribute/photosphere/
http://digiday.com/platforms/google-tracking/
I find it odd that stories like that don't get much exposure on HN unlike negative stories about Apple, Facebook, Microsoft etc.
They are. Selling ads is basically the only way Google makes money.
It'd be nice if they at least offered the option to pay $X/year to use Google services without tracking. But I think that would be unlikely, because it would highlight the value of the data many people give away freely.