Am interested in making a wireless home energy monitoring system. The project flow is as follows,

It is directly connected to the main supply of the device or the main electric meter

In case of Three-phase supply the device must be connected to each phase to record the power usage separately

The device consists of a transmitter where the power used is transmitted to the receiver constantly

The wireless connection is either of zig-bee or wi-Fi (cost & efficient basis)

The receiver is connected to a display where the collected data is shown

ARM processor (or Arduino board) is used to process the received data before it reaches the display

The processor must display,
1. The power used
2. The cost for the respective power used, it also must change based on the no. Of units used (with respect to govt. norms)
3. Average monthly bill based on the current power usage
4. User can set an alert when crossing a particular no. Of units, so that they can regulate their usage
5. It also consists of separate usage for each phase in a home
6. The data must be connected to a server, where the user can get analysis on their power usage- a phone app or facebook app

I need help on various topics like,
- Which SOC can be used for energy monitoring?
-Which technology can be used to make it compact?(ARM/ATMEL/ARDUINO)
-Which wireless technology can be used so that it is cost efficient as well as covers larger area?