Some of the coolest custom Android development to happen lately has come from the folks that make Paranoid Android. Since the launch of Facebook and their cool Chat Heads feature, PA has launched their own HALO code that allows for similar floating notifications in their ROM. Up until today it has been a PA exclusive, but they have decided to go open source with the project.
Luckily for all us ROM users this means that if our developer wants to poke through the code for HALO they can implement it in their own builds. This means that the awesome floating notifications can be used by more users and in different ways. Give it some time, but you will be seeing this as a main feature in many ROMs going forward. Be sure to check out our hands-on with HALO to see how awesome it really is.