Maybe a little too simple for what you're looking for, but came across the Battery Bug from
Argus Analyzers. Don't recall what I have on Grey Goose, but what I liked about Battery Bug was the constant monitoring and alarm feature should your the batteries charge state fall below a certain level. The Battery Bug also monitors the condition of your batteries and is extremely easy to connect. I was thinking of adding one only for the alarm feature. My current solution uses an analog meter and only has a momentary on-off toggle, so basically only monitors when I check it. The Battery Bug is available for around $40 and can be connected across a bank in parallel.
Worth a look perhaps, but this is not an endorsement as I have not used it. Not to hijack, but would be interested in any else's opinions or experience with this device.