There are some other alternatives. HTC had a lockscreen API for a while. Similarly, generic Android has started supporting widgets on the lock screen, basically. One of the evangelists even has a popular widget lockscreen with extensions called DashClock that many people are writing for.

Lastly, I haven't tried it, but I suspect replacing the Android Launcher would also let you do it. This is the method Facebook used for putting their talking heads in every app.