I've seen this on other servers, and it's pretty cool in my opinion. As far as I know, it's pretty easy to implement as well. (don't quote me on that)
So, for example, when you killed somebody with a bow, it would say how far the arrow travelled in the death message. For example, it could be like this:
Player1 shot Player2 from 32.5 blocks
How I (think) it could work:
1. When somebody shoots a bow, record their position.
2. When somebody gets hit with an arrow, record their position.
3. Check to see who killed who.
4. Subtract X coordinates, Y coordinates, and Z coordinates. Add them up to get the length of the shot.
I can elaborate if needed.
So, for example, when you killed somebody with a bow, it would say how far the arrow travelled in the death message. For example, it could be like this:
Player1 shot Player2 from 32.5 blocks
How I (think) it could work:
1. When somebody shoots a bow, record their position.
2. When somebody gets hit with an arrow, record their position.
3. Check to see who killed who.
4. Subtract X coordinates, Y coordinates, and Z coordinates. Add them up to get the length of the shot.
I can elaborate if needed.