Resource Pack HUD (otherwise known as RPHud) gives content creators the ability to mess with the in-game HUD without needing to write their own standalone mod. This is accomplished through the execution of RPHud scripting files, which are loaded from resource packs. Using the simple, quasi-functional language, it's easy for anybody with a rudimentary grasp of algebra to build a HUD like this:
I'm a user! How do I use RPHud-enabled packs?
Just about the same way you would use any other pack. Equip any RPHud-enabled pack, and the uppermost pack with RPHud support will be used to augment the HUD.
Where can I find some RPHud-enabled packs?
I'll probably build an index of RPHud packs if enough people are interested and enough packs are created. For now, though, you can find a few packs here: