Just some more information on CurrentCost Envi-R for the others (it was what I had before I switched to OEM), it is actually a two part system with a wireless transmitter and indoor display console. So the CT is connected to a “transmitter box” in the meter box (running off 3 “D” cells) with a base station inside the house which has the display and the serial connector for getting data off the display, in the same way an emonTx would talk to an emonBase.
So if @Zarch wanted to replace the Envi-R with the closest OpenEnergyMonitor equivalent, it would be an EmonTx in the meter box and an EmonBase plugged into his Pi (assuming he’s prepared to plug a “shield” onto his Pi instead of using the USB serial port). If a physical display is also required, then something else would be needed to fill that gap.