Apple's Keynote app is a simple way to create motion graphics for use as animated overlays in Ecamm Live.
Here are some steps to do this:
Add your slide text and animations.
Ensure that your slides have a transparent background. The background will appear black in Keynote.
3. Once you've prepared your animated slides, choose Export To -> Movie from the File menu.
4. When exporting, be sure to choose Custom from the Resolution, menu which will reveal a Compression Type setting.
5. Choose Apple ProRes 4444 in order to enable a transparent background.
6. Add the movie file to Ecamm Live as an overlay.