javax.servlet.ServletException: Something happened
Well they can collect data while the app is running, but as I understand it the app can't do anything when you Force Stop it until you restart it, or you reboot in which case it can once again be woken up by any events it is listening for (including the reboot).
You can also Greenify it (I am rooted, though I understand Greenify still works unrooted I don't know how well) and that should have a similar effect every time you turn off your phone if the app isn't in the foreground.
"Oh yes, I thought of something," panted Ford.
Arthur looked up expectantly.
"But unfortunately," continued Ford, "it rather involved being on the other side of this airtight hatchway." He kicked the hatch they'd just been through.
It is not every question that deserves an answer. -- Publilius Syrus