It is not possible to do as you please in the background. You have to conform to protocols by Apple. Unfortunately Apple doesn't let you run NSTimers on the background (there used to be an exploit in iOS 6, but they fixed it), instead you are given a set of instructions you implement to get the location updates.
Read this article by Apple, it thoroughly explains how to run app in the background.
For your sake, I'd recommend implementing APN service on your server and push to the phone when needed - 8AM in your case. It has its cons, but it's the only way I can now think of.