LockLauncher is the best Lock Screen Widget Builder.
Create your own Lock Screen widgets and actions using symbols, app icons, and custom images.
Each widget can open any URL you want; there is a list in the app to select from and you can add your own if you wish.

For example:
- Select an app icon
- Add the URL to open the app
- Add the widget on the Lock Screen (tap on the widget to edit it)

Pressing on the widget will now open the app directly from your Lock Screen!