They were going to be integrated into agUF, then you'd only need SmartyCat (not the mana bar itself) I think... Don't remember if this got finished yet, though. I haven't played my druid in some time.
EDIT: but you could use both and at least have it match your agUF frames. I had mine placed right under the mana bar (I don't use the casting bar on my player frame), with the same width, texture, border, and only had it show while shape-shifted.
What I did here is moved the SmartyCat bar over my rep bar and have it visible only when I am shapeshifted. I know its not the end all solution A LOT of druids are looking for with AG Unit Frames but, for now, it is a pretty usable solution.
I'm not sure how difficult it would be for someone to write a mod that could override the colors/values/text of the xp bar to do something similar to what I have setup but that would for sure be awesome :)
Oh yeah, I also modified SmartyCatBar.lua Lines 81-82 with: