This is very niche, but I haven't seen this feature in any mapping apps that are commonly used for ground search and rescue.
GPS receivers are starting to be more frequently used for SAR missions to download search team data when they get back to base. Search managers get a nice idea of where teams have been based on track logs overlaid on digital maps.
There's a bit of a controversy in the ground SAR community right now due to a recently released government report that's quite critical of traditional ground SAR techniques. (Mostly because scientific search theory has never been applied as it has been in marine searches.)
Anyway, after reading the report findings, it would be useful to have an option to apply a fixed width to a track, and display it on a map. For example, you have a 5 person search team with 10 meter spacing between each member. The team member in the center is logging tracks. When the team got back to base, the search manager could apply the spacing value that was used by the team and display a track path (actually two lines) that define a 40 meter (or whatever) swath that was searched. (Yes, I know, the precision of the swath will vary depending on a number of factors, but this would be a nice ballpark tool for quickly seeing search coverage.)
Just a thought. TF has some real nice features that could be pressed into service for SAR work...
Joel