Here's a little preview of what the HUD will look like. The drawing, scaling and colouring code is essentially complete at this point. Remaining tasks are:
(Easy) Linking in the existing health detection code to colour the items automatically.
(Easy, but will take a bit more time) Changing the code to only display the graphical HUD when you have a nanosuit or quantum suit helmet on - without it, you're only getting a text display accurate to 10%.
(Harder, but I see a way to doing it now) Adding in a scaled text display to write the item names and percentages alongside the HUD, with lines leading to it. Tricky, but after poking around inside Tesselator.java and FontRenderer.java, I might be able to create scaled text.
Item colours: blue for full charge/health with a smooth transition to red for critical damage/charge level, white for invincible armour (eg. solar helmet), black outline for no armour. Arms represent the status of the currently equipped tool.