The implementation of linear referencing in field maps is very close to our needs. What's missing is being able to measure continously, that is to see the section numbers increase while you move along the reference line, and - at the same time - see the distance perpendicular to selected line.
Our lines also have heights. The height corresponding to the section your at (or want to be at) is very interesting, and should be an easy calculation.
It would also be nice to measure the same data with point-and-click on screen. That is, the needle you pin-point will have information about section number and distance from line (perpendicular).
Use cases for these ideas is to be found in road construction projects and pipeline projects by those who do the construction work. I've read some earlier ideas about differing if you're left or right of the line. We're used to that when youre left of the line, distance value is negative, and positive if you're on the right-hand side.