Unlock different Apps from lock screen I just got the Galaxy S6 and am new to Android.  Is there any way to have the phone open a different app/program, depending on how I swipe open the lock screen? 

I.e. if I go up, right, up - open Music.  If I go left, down, left, open Chrome, etc.
I've mentioned below some use-cases tested on Android 5.0.2. Choose the one which suits your need.

GMD GestureControl

It needs root access. It can launch an action (say music app) using gesture from any app opened on the screen including lock-screen. 

Usage instructions


Install and launch the app.
Tap Menu key and select Settings. Choose Device Setup at the very end of instructions if the gesture doesn't work.
Enable Start on boot to get rid of the need of launching this app manually to activate gestures on lock-screen or system-wide.
Create a gesture by tapping Select Gesture.
Choose which type of gesture you want, be it curvy (select Record Gestures) or the simple straight directional ones.
Unless you chose Record Gestures, the step would be to tap the direction icons to record gesture.

Touch Point: Mention the  number of touch or fingers you would be using to make the gesture
Anywhere: Location on screen where the gesture would work
Action: Choose the action to be performed like launch of an app, once you're done making the gesture 
Per App Action: Mention where do you want your gesture to be activated. Default is everywhere


Go to Action.
Choose Application if you want an app to be launched.
Choose your app.
Go to Advanced options.
Enable Activate on Lock Screen.
Save and apply the changes.


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I tried this app with CM12's default screen lock and third-party SlideLock Locker. The result is that the gesture would execute the action if you perform the gesture on lock-screen but you can't see anything unless you unlock the screen if Password/PIN/Pattern or any security measure is set. 

Nevertheless, it is a very powerful, intuitive and useful app.

GestureLocker

It doesn't need root access. Last updated in 2013, yet surprisingly, it worked on my device without hitches. Also, it seems that unlike traditional lock-screens it simply creates an overlay on the screen (with a lock icon) and your opened app  would continue to be visible but non-interactive unless you perform the unlock or other user defined gesture.

Usage Instructions


Install and launch the app, and uncheck Show LockScreen Gesture (it hints your gesture on lock-screen).
Uncheck default gestures and tap Add Gesture. 
Name and record your gesture, then tap the newly created entry.
Select the app which you want to be launched using the gesture.


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Notable mentions


Gestos - Gestures -- last update an year ago, so it didn't work satisfactorily on Lollipop. But it may work nicely on Kitkat or prior Android versions.
Pi Locker -- it is a regularly updated lock-screen app and has some inbuilt gestures with no support to add user gestures as of now. I noticed some glitches during usage but that may be device specific.
Locker Master- Fun, DIY Themes -- you can create your own custom lock-screen without any programming I believe. It required internet connection to work satisfactorily and I dropped this idea considering its hunger for app permissions. 




I've compiled two videos (ripped) to show the two main apps in action, both of size ~6MB:


GMD GestureControl
GestureLocker


Cheers!