Anyone use the iConserve Elite Wireless Energy Monitor on their NEMA 14-50?

[HankLloydRight]

I'm looking at getting one of these to monitor the KWH consumption on a 14-50 we're having installed:

ebay: Iconserve Elite Wireless Energy Monitor with 2 Sensors | eBay
electroflip (same product): Electricity Monitor - Power Saver

I'm wondering how easy was installation and how accurate is it?

edit: Or this Efergy Elite Classic: elite classic - home power monitor

thanks.