What is this nose cowl mounted display?
This is a GPS guidance indicator from AG-NAV, with the main unit visible onboard. Snapshot from your linked video:


Main unit

Using the main unit, different information can be displayed on the lightbar:


GPS cross-track
Angle of Intercept
Overlap in sprayed area
Area already treated
Spray height
Aircraft inside/outside area indicator
...


Basic data can also be shown (e.g. airspeed) See this video. The indicator itself:


Lightbar

More:


Lightbar brochure.
Main unit brochure.