Thanks for all the replies.
What I am actually wanting though is to be able to see the amps being drawn and put back into the battery bank rather than show a state of charge or accumulated amps totted up/down.
Reading the Smartgauge write up, they do seem to have a point.
Is there any decent simple good digital amp meters available ?, or can the NASA, Sterling & Victron models be used this way ?
There are a lot of cheap prices amp meters with shunts on ebay, any good ? e.g. http://www.ebay.co.uk/itm/200V-200A-DC-Digital-LED-Amp-Volt-Combo-Meter-With-Shunt-for-HHO-EV-car-Solar-1-/161036443632?epid=1131939908&hash=item257e851ff0:g:s1MAAOSwnsZZgCfP