Just stumbled across this review of the emonPi from a nice guy called Mike:
Thanks Mike 
We have no affiliation with Mike and are not paying him…honest! I would love to find some contact details for him to say thanks but I’ve not been able to find any, other than leave a comment on the video.
His DIY power-wall battery store setup detailed in his other videos looks rather impressive. I would love to try and build one myself.