MapTool uses "Waypoints" to measure around turns and corners. This is obviously helpful functionality that I really miss in Roll20. I'd love to see it added and I am certain that it has been mentioned elsewhere, read on.
It occurred to me that with a slight modification, waypoints could increase the utility of even straight-line measurements!
Let's say, for instance, that a waypoint is dropped by pressing the space bar while measuring. You could specify *other* waypoint tools that would alter the measurement in helpful ways. For example, pressing Alt while measuring might drop a waypoint and double all measurement after that waypoint until another Alt waypoint is dropped.
The ability to measure double movement for a span would help with a number of games that modify movement or cover for a span. The conventional way to approach this is to try and include movement rules on the map, but I think this system is much simpler and more versatile!