I recently found the Health section on my IPhone; I was surprised at how much information it gathers passively just as I walk and sleep; this, together with my BP app and cal counting app have been very useful. I may get the Apple watch next as I'm due an upgrade.
-@Cynic
By default, my Samung decided it would butt in and tells me how much I'm using my phone. It also monitored where I went and how long it took me. Google maps also presumes I'm in certain places and asks me to give reviews.
I've disabled all that. They should mind their own business!