Any thoughts on Kefir water?
A couple of years ago I used to brew up some kefir *coconut* water, using the coconut water from young green coconuts (got the instructions from the BED book). It made a great tangy pro-biotic tonic, but was way too labor intensive to make on a regular basis, not to mention it was a big deal trying to score the young green coconuts where I live. I've always thought I would return to making it again if my schedule ever settles down a little -- IMO it's a nice non-dairy alternative to regular yogurt or kefir, and it would seem to be primal enough.
[Also, most of the time I would scoop out the coconut meat and separately culture that -- made a really nice coconut "cheesy pudding". This added a *lot* of time to the process for a very small amount of end product, but it sure was good!]