App Switcher for iOS is a fantastically clever hack in the form of an official App Store app, let down slightly by a very poor UI which makes setup tricky.
The app does one thing: lets you launch apps, send emails and call people, right from the pull-down notification center on the iPhone and iPad.
It manages this by using URL schemes. URL schemes are what allows apps to pass info to each other in iOS. If you add a "g" before a URL in Safari and hit return, for instance, it will open the page in GoodReader. The app lets you add the URLs of your choice and then presents them as permanent entries in the notification center.
Thus, with a couple of swipes you can be reading a book in the Kindle app, managing your Bluetooth connections or sending a quick e-mail reminder to yourself. It's similar in scope to Icon Project, an app which helps you to add URL scheme shortcut icons to the iOS home screen, only it's way more useful (Here's a handy list of URL schemes to try, courtesy of the iDownLoad Blog).
It will also work from the lock screen.
Setting up the app is a pain. You first need to create various URL schemes, and then you have to assign them to one of a maximum of four slots to be shown in the notification center. You can also opt to have a shortcut to the "Quick Launch" screen, which opens up a screen of tappable shortcuts within App Switcher.
It's set-and-forget, though, so both the annoying setup and the fact that you need to run it pixel-doubled on the iPad can be forgotten, if not forgiven. The app is just $1. I recommend grabbing it ASAP, as this is just the kind of thing Apple likes to remove from the store.
App Switcher product page [iTunes]
