One important thing for a rover, esp. one that is capable of moving beyond line-of-sight is management/tracking of power. I've known I wanted some sort of networked, data-reporting battery and power management system. I feel like I have the software side of things down pretty well and electronics is sort of where I come up short. Fortunately, digging around on the Intercats for "Open Source battery monitor" or "ROS Battery monitor" or something similar, led me to this ROS-aware Battery Voltage Monitor.
The circuit itself is a big network of voltage dividers, which even I know how to put together, so not too horrible to put together over a weekend.
and the final realization installed on Tenacity, complete with readings off an 11.1V 5000 mAh LiPO battery shown as a ROS topic.