Any third-party Windows Phone 8 app may work in the background with this simple trick
Now that Windows Phone 8 is here, has multitasking been improved? You bet! Certain apps that need to work in the background are allowed to do so – that includes VoIP applications or apps that track the user's location, not just the music player, as the case was back in the days. Moreover, an app that is already running will not restart when the user re-opens it from the list of apps or by tapping on its live tile. However, there's a catch.
The behavior we just described is valid only for stock applications, such as the Pictures Hub, the email client, and the likes. When you tap their live tile, they spring back into action right where you left off, instead of starting from scratch. Yet developers of third-party apps can teach their apps to do the same trick, as it has been revealed. They simply need to mark their applications as "GPS apps", and the system will allow them to run in the background. Whether apps that use this workaround will be allowed in the Marketplace is a whole different story, but it is good to know that a way to fool the system is at developers' disposal.