Haha, this idea is a very general one, as meters can be used for many different things. I also wanted to state that like the old Energy-O-Mat, it would produce a Redstone output as long as energy is passing through. (As someone mentioned). Thanks for all of your support.
Having this in an addon would be great! I'd be elated if it was even put in IC2! HAYO! 
I was messing around with a few of my friends on an SMP server, and we weren't quite satisfied with the 1IC per 4000 EU power rate for the Energy-O-Mats. I preferably use them just for the redstone output since from server to server, the economy and inflation rates vary greatly.
We wanted to sell power to "customers" and charge them based on their energy usage vs. OUR rates. Thats when I got the idea "Hey, there should be a machine that logs how much EU passes through it", then we can charge these energy hogging towns the proper payment.
So I present to you, my idea proposal of the "Energy Meter"!
Description: A machine that can take inputs from all 5 sides, where the output being the marked face (like other machines). This output face can be changed using the wrench. Using the wrench on the output face will dismount the machine. As EU passes through the machine, it logs both the total EU that passes through, and the instantaneous EU rate (in ticks or seconds) of the combined inputs at that time. In the gui, you can also clear the data, although only the owner of the block would be able to do this. (I have no idea if that is possible, maybe it works the same way as personal chests. However in this case the owner would get a gui with the clear button, while other people don't have the button). It would act as the old relays did, where all power is brought in from the inputs, combined, and thrown out the output face. Handles LV? MV? (not sure if so..)
Crude GUI Idea (Just to give an idea of what the gui would look like, although this is very crude)
Crude Texture (mock up of what it might look like?)
Usage: Probably only used for multiplayer, where people could see how much energy someone is sucking up and charge them for it. Or just as a nice way of seeing how much energy your nuclear reactor has put out in your singleplayer world. As for multiplayer, this lets people charge customers by their rate where they could just check the meter every so often and charge for how much was used. Also a nice way to see if your roommate is hiding a Mass Fabricator in your basement 
Another thing to think about is if you own a town in SMP, you slap one of these on every home (like in real life) and you base your taxes off energy use!
This is just a basic idea, feel free to comment and improve on the idea, maybe give a possible crafting recipe idea. Nothing here is absolute, so I'm sure things are subject to change.
I love working with IC and BC. Redpower just adds to the fun Hope to find a nice little plot of land and start working towards a reactor facility 
IGN: Master_Kyle
Loc: East Coast, US (Just so you know when I'll be on)
