There are 2 ways of updating the tiles.
- From within the app (or background agent)
- From a remote service, via push notifications
The method with the least impact on the battery is to send push notifications when there is a new article. This does require a backend service capable of identifying when new content is posted and sending the push notifications though.
If you want to do it all on the device using background agents, the important thing is to remember to not pull down all the content each time. If you have control over the backend then add the ability to return how many new articles there are. If not, only pull down the feed if necessary. Look at the If-Modified-Since
header for one way to do this.
It's very easy to reset/clear the tile contents from within the app when launched. When you navigate forwards into the main page is normally the best time.