I am working on the dxfeed implementation in MT. Should be released to our users fairly shortly. As for MT streaming API being used in Motivewave - it can be used by anyone who can do Websockets with JSON or XML. It allows you to connect to any of the data sources from MT and subscribe/unsubscribe to market data from them, as well as connect to any of the supported brokerages and trade/monitor your accounts.
Full MT functionality, but available to 3rd party software. The API connects to MT locally on your computer (MT can be reduced to just a hidden Dashboard window), and provides a simple interface hiding all the complexity of the dozens of APIs that are used to connect to various sources and brokerages.
Send me a PM here if you want the API doc.