Whats Going On?
There have been more than a few attempts at making a Sugar compatible video chat application. As it stands right now there are at least 4 or 5 that work to varying degrees. Empathy is probably the most functional app that I am aware of, however, Empathy is not Sugarized (as far as I know). So after signing up for a bunch of different mailing lists and asking a bunch of questions here is what I have learned.
Build a Completely New Program
After talking to the development lost for sugar, it seems possible to build an app in entirely C code that can interface with sugar through DBUS. DBUS is a IPC messaging system that many Linux systems use. If an application implements certain DBUS interfaces then it can be "sugarized". So how hard would it be to implement a DBUS interface in C? Well according to the API docs, pretty hard: http://dbus.freedesktop.org/doc/api/html/index.html. Apparently you would be in for a world of pain. Thats not terribly surprising given the nature of C coding and the type of functionality that DBUS exposes. Thats just one part of the project.
Next there is Telepathy. Interfacing with telepathy doesn't look too bad. The docs appear to be somewhat here and there, however, which could lead to some pain. However, the telepathy-devel mailing list is responsive and hopefully willing to help if any telepathy interfacing needs to be done. And last but not least: gstreamer. Interfacing with a telepathy client would require some gstreamer code (I think). I am not completely sure how much back end stuff is handled by telepathy at the moment. Certainly implementing an RTP/RTCP stream with session control would be a major pain and time commitment. Especially since at the moment it is certainly in the pipeline to implement both audio and video streaming (a natural expectation for a video chat service).
Maybe There Is An Easier Way...
Since Empathy does by default run on the XO platform it should be possible to Sugarize the Empathy client. First some pros to this idea: all the low level mess regarding RTP and video streaming would be handled by Empathy/telepathy, account management would be handled by empathy, basically everything would be handled by Empathy (how nice), and it would be (I think) relatively easy to integrate a Sugarized Empathy client into the Empathy RPM package for the XOs. Now the cons: the Empathy code base is not easy to dive into. After briefly looking at the code, it would seem that there is just so much stuff going on. Native GTK in C is not exactly the most concise of GUI code (but I am sure its very fast). Thus learning the code base and actually adding the required DBUS interfaces for Empathy to interact with Sugar would be in all likelihood rather difficult. But not impossible.
What To Do?
Well, those are my options. Either way I am going to need to really understand DBUS in order to implement the required DBUS interface for Sugar. The question is do the pros in making an Empathy based client out weight making a new client from scratch. Time wise, will learning the Empathy code base be feasible? So... In the next week I am going to commit to one of the paths once I have some more insight from the respective mailing lists and people involved in Empathy/telepathy and Sugar.