iOS doesn't support custom pop up windows outside of your app. Which means for an IM app you need to be running it for a popup to appear (sort of making the who

iOS doesn't support custom pop up windows outside of your app. Which means for an IM app you need to be running it for a popup to appear (sort of making the whole popup window pretty useless IMO). On Android you can display a custom pop up window even if the user is not in your app.