Is there any API documentation available that I can use to integrate NzbDrone v2 into another app (ie. HTPC Manager)?
Thanks
not right now, but its definitely on the list.
All UI functionality is basically driven by our API so you could technically take a look at network tab in firefox or chrome dev tool as look at the calls and response. I know it’s not perfect but we haven’t had time to document the API yet. but it will be done.
ok no worries. I’ll try to figure it out the hard way 
Thanks for the great product!
Feel free to ask here or on IRC if you run into issue or have more questions.
Thanks. Is there any api key implementation for 3rd party app communication?
No API key yet, its all secured by basic auth (when configured), though we do need to add the API key, sooner than later it seems.
What would also be cool is an architecture doc with basic info on how it all fits together.
Even something high level to start with just to see the tech stack and what you might need to become familiar with if you want to dig into the code.
@faush01 the readme.md does contain some of the high level pieces NzbDrone uses, but we should add a how to contribute readme.
@hpooni - API key is being added to the develop branch shortly, instead of basic auth. The key will be shown in the config file only right now - https://github.com/NzbDrone/NzbDrone/wiki/Release-Branches
@faush01 - Added information on contributing to the wiki - https://github.com/NzbDrone/NzbDrone/wiki/Contributing