If you're going to do this you have to consider the ramifications of how stale the information on the card becomes over time. The example, showing a "Checked in since..." will become stale if someone checks in/out on another device.
A real iOS 7 API to update these cards in the background would be a nice addition.
I don't know if that's how other people perceive it, but it does feel extra-wrong when you hack it to try to convey timely information in the switcher.
I think this is an undocumented notification, so it's possible other iOS versions will break this feature.
A little less cynically: If you can redesign a screen in the app to remove clutter and highlight the important information for the user for the app switcher, why don't you do that in the app? Sounds like it might be a better UI design. Now, I can think of many reasonable counter examples, but I'd challenge you to spend more time on the app UI where your users spend most of their time.
It's not that simple. The problem isn't information density/clutter. When in task switching mode the screen is very small so just being able to make the most important information larger so it's easier to read is useful. Also, there may be buttons on screen that may be important features - but they aren't important in task switch mode as they can't be pressed so removing them and making more room for the content makes sense.
It's like designing for a small screen device and a larger screen device. You can make useful features easier to access on the larger screen due to the extra real estate. That doesn't necessarily mean you're cluttering the UI.
As an aside, is there anything similar to this for android? I've tried a fair bit of googling but can't find anything or the right search term.
[1]: http://developer.android.com/reference/android/app/Activity....
[2]: http://commonsware.com/blog/2012/01/16/secure-against-screen...
[3]: Use android:excludeFromRecents="true"
