I find the motion sensing and gps tracking to be the creepiest. Using motion sensing they can know when you put your phone down and pick it up, if it was screen down or face up, and knows when you are walking, running, driving, etc. Combined with GPS it can be used to pretty accurately judge when you wake up, where you go, and how you get there. Lots of apps also don’t “close” when you swipe it away, they continue running in the background, so if you have the setting “only collect data when using the app” it will still collect data until you close it in the background or force stop it.