Sorry for the silence on my part, I've been focusing on the coding.
This feature requires a bit of development work on our end -- basically, we have to implement a system for polling streams very frequently in a way that doesn't hammer the streams and degrade server performance, while still being able to quickly notice track changes so we can promptly update the track info. This underlying system can be used for a great deal of other things, however, so I began implementing it a short while ago.
Up until the (potential) discontinuation of SHOUTcast DNAS became a possibility, this was actually my main development project, but it's been sidelined for the time being as we're fast-tracking a few features deemed essential in the event that the SHOUTcast toolset is indeed abandoned.
So in a nutshell -- support for tunein.com (and potentially any other directories) is already in development and will definitely appear in a future release. We just don't know quite when it'll be completed just yet.