I realized that I totally forgot the space scanner part of the planets! So I took time to implement them, and to fix up issues related to it (such as able to select invisible fleets, seeing other fleets not in range between turns, etc). I also even added a scanner range visual indicator, by pressing "R" (similar to Fuel Range's "F"). I changed the fuel range to be green, instead of empire color, and radar to be red.
Here's a screenshot with me using Deep Space Scanner technology. Note, fleet's radar is actually centered at the system they're in, otherwise they'd be centered on the fleet.