The ME Network Monitor is a block added by IC2 Nuclear Control. It is only craftable when Applied Energistics 2 is installed. The ME Network Monitor can be connected to an ME System. It will not add special functionality to the ME System, however, it is needed for the Applied Energistics Monitor Kit, assuming you want to monitor the number of bytes and the number of item types, rather then the item/items crafting currently and the amount of those items crafting currently. In the later case, the Applied Energistics Monitor Kit should be used with a Crafting Monitor instead.