1) Right Weigh Scales.
2) Air Pressure Gauge in enclosure.
Right Weigh Scales
Air Pressure Gauge
The Nissan UD fleet of trucks with airbags are suitable for this type of application.
Where more than one airbag ride control valve is fitted some additional piping and valves are required.
This could be the case with some of the three axle trailers.
Here is the photo of the Nissan UD airbag suspension and the ride height control valve.