We actively maintain and release new features as they are published. While we don't provide a full out of the box pipeline (yet!), there are plenty of examples and documentation which walk you though the math, implementation, and other issues. If you want to read about the graphical models underlying GTSAM, see [2]
Utilizing OpenCV for feature detection and association is pretty much all you really need to add to a program in order to recreate Photosynth using gtsam. I'd also you recommend KAZE features from a former post-doc out of our lab, it's state of the art and recently added OpenCV wrappers[3]. However, it's also trivial to integrate other sensors such as IMUs, GPS, lasers, etc. for full navigation problems.
If you wish to know more about the actual subject, I definitely recommend Hartley and Zisserman's Multiview Geometery Book[4]
[1] https://borg.cc.gatech.edu/borg/
[2] http://www.cc.gatech.edu/~dellaert/pub/Dellaert06ijrr.pdf