Then you might be interested in my application that I posted here the other day. It's mainly a GUI application for power users, but it also has a console application so you can integrate it into your workflow. The JSON support I had added as an additional feature, but to my knowledge it is not used by anyone yet (at least I had no support mails about it). Oh, and it works without cloud and can be used completely offline (after one-time online activation, if you want to remove the demo watermark).
https://news.ycombinator.com/item?id=31999358