Object tracking ignoring distance to object

[reger24]

Is your feature request related to a problem? Please describe.
In object tracking mode, robot follows person with preset speed but only stops if tracked object is lost (robot w/o sonar).

Describe the solution you'd like
Adjust the speed by a estimated of distance. This could be implemented by measuring the box width of the tracked object.
Under the (true) assumption that tracking box width is large if close to the tracked object and small at a distance.

Describe alternatives you've considered
IR or sonar distance measurement could perform a emergency stop, but it's not the same as controlled slowing down.

Additional context
Additionally this could help to adjust speed to the movement of the tracked object