So I was watching this awesome video just now, and wondered if the same system could be used to calculate phase angles between your parent body and your target body.
This is the next step I want to take in KSP—learning to calculate phase angles by hand, since I've done it enough times using a computer (I'm more of a "lots of math and notebook paper" type of KSP player). I think this could be a pretty cool way to do so.
Anyway, so I'm wondering if it'd be possible to use this measuring system, where the center of the sight is the body whose SOI you're in and you're in a top-down view of the Kerbolar system.
I think it'd be a neat tool to actually build, either physically, or in software. Software would be particularly awesome—just a basic window that accesses the planetary positions from the game time, and has the user rotate the spiral marker. Then it'd crunch the numbers. It's obviously not practical when things like KER exist, but I'd rather learn to do this stuff.