Otto is an event bus designed to decouple different parts of your app while still allowing them to communicate efficiently. Forked from Guava, Otto adds functionality to an already refined event bus as well as specializing it to the Android platform.
auto-parcel is a port of Google AutoValue for Android with Parcelable generation goodies.
BillingProtector is a small Android library aiming to check the device state & purchases security. Its main purpose is to block a transition if the application has been modified or patched; it can also be used to prevent applications from being executed on an unprotected/insecure environment.