I'm looking to write an application which allows an alternative lock screen for Android. I've seen posts around here on SO as well as applications in the Play Store, but I can't seem to find any APIs for doing it on developer.android.com.
How do you write a replacement lock screen for Android?
To summarize what others have said on here and what similar questions have asked:
TL;DR No, you cannot easily write a replacement for Android's lock screen.
The longer version: In order to write a lock screen replacement, you'd need to either create a custom ROM which bundles your lockscreen or you'd need to wade through undocumented Android and device-specific APIs to work around this problem. Here's hoping that Android M will allow us to write lock-screen replacements.