There isn't anything in oUF (yet) to support burning embers or demonic fury. However, it's not because it's not "that necessary"; it's simply because the author of oUF has not had time to work on it.
Demonic fury is just a second mana bar, very similar to the druid mana bar. You should probably have it change color while in demon form, like the default UI, so it's one color while you're filling it and another color while you're using it.
It is important for burning embers to be statusbars, or at least have some indication of how close you are to filling the next ember. My solution for avoiding the "is this bar full?" issue is to make the bar semi-transparent while it's filling, and then switch to full opacity when it's full. This way you can still see its progress, but it's noticably dimmer when it's not full.
If you want to see how other people have implemented support for these powers in oUF layouts, check out
oUF_Phanx,
oUF_Diablo, or the
oUF_WarlockSpecBars plugin.
If you like the default UI's appearance for burning embers, you could actually just pull the burning embers off the Blizzard player frame and put them on your oUF player frame.