Starting an app when the screen is locked? Is there any easy way to start an app when you press the button to lock your screen? I've seen custom lock screens before so I know it's possible even if I have to make my own app for it. I have an app that I want to pop up every time the screen is unlocked, but it doesn't do it on it's own. I've seen/used other apps that could do this so if necessary I would code my own app to do this, but I'd prefer an already existing, preferably free option.
There might be multiple solutions to this. One I can think of involves the use of Tasker, the most flexible automation tool for Android. You could create a profile that triggers on "Screen Unlock", and have it start an app.

However: though there's a free 7 day trial available on the projects homepage, after that the app costs about 5 Euro. There are many other automation apps available on the playstore which might be able to achieve the same. As a long-time Tasker user I no longer try the others, so I cannot tell for sure.

Condition: Event &rarr; Display &rarr; Display Unlocked
Task: App &rarr; Load App &rarr; (select your app here)