I’ve just created this simple Android library, inspired from the recent changes to the Google+ app, which introduced a floating action item to the bottom. In G+ the action item appears and disappears based on the page scrolling.
In the same way I’ve created this library, with some more customization options, like the gravity and direction of the floating menu items.
Here’s a video of a sample implementation:
Source code and documentation can be find on the github project page: