From OpenEnergyMonitor Wiki
emonTx SMT
Tech Spec
Powering the emonTx
CT Energy Monitoring
Current Only (Apparent Power)
Voltage and Current (Real Power)
Reading Directly from Utility Meters
Pluse Counting
Optical
Wired
IR Interface
Elster
Connectivity
Wireless
RFM12B (Default)
XBEE
XRF
Simple ASK RF
Wifi - RN XV
Ethernet
Wired Serial Network
Open-Source Design
Expansion