iOS: Keep application running in background

How do I keep my application running in the background? Would I have to jailbreak my iPhone to do this? I just need this app to check something from the internet every set interval and notify when needed, for my own use.

Yes, no need to jailbreak. Check out the "Implementing long-running background tasks" section of this doc from Apple.

From Apple's doc: Declaring Your App’s Supported Background Tasks

Support for some types of background execution must be declared in advance by the app that uses them. An app declares support for a service using its Info.plist file. Add the UIBackgroundModes key to your Info.plist file and set its value to an array containing one or more of the following strings: (see Apple's doc from link mentioned above.)

I guess this is what you required

When an iOS application goes to the background, are lengthy tasks paused?

iOS Application Background Downloading

This might help you ...

Enjoy Coding :)