GridStatusShield 

Note: Because of the ability "Savage Defense" of feral druids the shield values for them will drop far to fast on incoming damage. I don't have a fast (or any) method to get the current attack power of the druid to calculate the amount absorbed by this ability.
Furthermore Blizzard changed the ordering in which shields are used up from the duration of the shield to the amount remaining (meaning small shields are used up before bigger shield). I didn't update GSShield for that by now because it still is correct in most cases because most short shields have a smaller amount (and I can't know the size of non-player shields anyway). Maybe I will implement correct handling of this at least for own Aegis and PW:Shield in future releases.

What it does

This addon provides a grid status which provides the remaining amount of your priest shields on a unit. It does only display the amount of you own shields (or at least tries to :-).
Some things you should know

How to activate

Just register the shield left status with any text-frame of grid.

Some things you should know

There is no "GetShieldLeft()"-method provided by WoW to use, so this addon works by evaluating the active shields and the "absorbed"-combat messages on a unit. When doing this the addon always assumes the worst case. So the remaining shield value displayed will be more likely higher than smaller.

An amount of zero displayed means either: 1. there is a shield but its not yours or 2. its your shield but GSSHield thinks all its amount is already used up which obviously isn't the case, but since GSShield always assumes the worst case this can happen often.

The addon does consider non priest shields, but only in the way that it doesn't reduce the priest shields values as long as there is another shield active which is before them in ordering (it doesn't have to know how much of it is left, as long as its there it will absorb the damage).
Some words to Multiple shields on a unit

Some words to Multiple shields on a unit

The addon assumes that WoW uses a strict order when there are multiple shields on a unit to decide whichs shields value to use up first. For now it uses the total duration of the shield as ordering (with priorisation for elemental shields). Meaning short shields will be used to absorb damage before longer shields. This ordering works for the mage shields as well as the priest shields. I whould be thankful for any definite information how they are really ordered.