Does NRG egg replacer work for stuff like meatballs or is it just for baking

I think it will work, but I don't think it is necessary. As Nozlee suggests, moist, shredding bread will work, so will a little bit of ground flax seeds. I don't know that the milk is necessary, I was thinking that tomato juice or thinned tomato paste might add more flavor.
I personally think that there are better natural substitutes for eggs than NRG- bananas, pumpkin, apple sauce, flax, chia seeds are options.

If you'd like to avoid adding eggs when cooking things like meatballs, you can add a slice of bread soaked in milk and then shredded. The purpose is to act as a binder without being too dense -- it's not like in a cake where it serves as a leavening agent.