I haven't seen a push for it outside of Meteor yet, but i'm sure that is one of the things that they would want to push for later.

Although, there are various DDP clients for other languages as you can see here: http://meteorpedia.com/read/DDP_Clients

(I work at Meteor).

There have been some discussions with Asana (asana.com) teams who are building their new data store with a DDP API published for their clients.

We use it to interface with our Django projects https://github.com/commoncode/django-ddp/

One example: https://github.com/whitesmith/meteor-motion

I'm writing an Arduino library at the moment as a small part of my thesis which I'll release.