Quite honestly, I don't get it. Why would anyone want their product to depend on a third party (= point of failure) for something as trivial as storing a string in a database and calling a markdown processor?
Hmm, still, with Postgres supporting XPath queries natively, I feel that your added value is rather slim, I must admit.. It doesn't have JSONPath, but it does have something else that comes very close (http://www.postgresql.org/docs/9.3/static/functions-json.htm...)
Sorry about that! Yeah, that's something a few people use to track & graph things (either y/n questions, 0-n question, or numeric questions) via scheduled emails.
I actually rather like it. I had a similar idea a year or two ago which became something more like a text snippet site, but I originally had ambitions along these lines.
Ping me at isaachodes at gmail.com if you have specific questions (and I've love to hear about your use-case as well). Encrypted data at rest and transit are upcoming (SSL is very soon, encrypted by the secret key (as an optional measure) is coming later, if there's demand for it).