I'm not sure I understand the Google Play store argument. If you're running on Android,Google already supplied you the OS, which would be a better target than some app.

So given that you are using Google code already, the "most trustworthy" source becomes the Play Store.

But Google does not write that code, and frankly given the volume of submissions (and obvious problems) by "most trustworth" I don't mean you should trust it.

Or to put it another way, once you start using code, written by someone else, the -source- of the code is irrelevant. It should not be trusted.

Which is true for your phone in general. It is not a "trustworthy" device.and you should treat it as such.