LSD-SLAM and Cartographer both support ROS so perhaps integrating the two would be fairly straightforward (using LSD-SLAM's monocular features with Cartographer for SLAM).
PL-SVO is also a very new and interesting approach to watch out for. They open sourced the stereo slam version and claim the monocular one is on the way.
For people interested, there are a couple of very interesting projects and studies on how to do just that:
* Direct Sparse Odometry: http://vision.in.tum.de/research/vslam/dso
* LSD-SLAM: https://github.com/tum-vision/lsd_slam
LSD-SLAM and Cartographer both support ROS so perhaps integrating the two would be fairly straightforward (using LSD-SLAM's monocular features with Cartographer for SLAM).