The ToroHUD project is forked from ToroHealth, but aims to provide more features at the cost of requiring the mod to be installed on both client and server.
With ToroHUD, damage given, received, or mitigated will be displayed as a number that pops off of the entity. Also, health bars will appear in the top left corner for the entity in the player's crosshairs. ToroHUD will also show any potion effects of a targeted entity.
The ToroHUD mod must be installed on both server and client. If you are looking for a mod like this one that doesn't require a modded server use ToroHealth. ToroHUD has the following advantages over ToroHealth:

Please feel free to include ToroHUD in any modpack. No need to ask for permission.