Ok, I don't think this idea has been suggested before and I don't know if I'm the only one who feels this would be useful, but here's my suggestion and the idea behind it.

Suggestion: A shield meter display on the HUD, that tells you the current health of your shield, as well as giving you a clear indication of how long your shield has left until it is fully recharged when it breaks.

When your shield is useable, the HUD will look like this, a simple blue bar which you can use to easily judge how much health your shield has left.
http://i287.photobucket.com/albums/ll136/joe_inky/ShieldA.png

When your shield breaks, the bar will turn red and slowly increase until it fills up, when it fills up, the shield is usable again.
http://i287.photobucket.com/albums/ll136/joe_inky/ShieldB.png

I think it's useful for judging how long until your broken shield is repaired and how much health it has left, it fits neatly into the HUD, and it would be incredibly easy to code.

Any thoughts?