So we have:-
Tyre pressure - useful, but a lot of aftermarket units are not reliable
Water level - not needed as I put a watering can of water in my outside fill tank for every bucket of waste aI throw away. When it go glub and spews over my foot I also know it's full.
Noseweight load - I have a premium jockey wheel that gives me the load. I also keep a book of weights and usual van loading with resultant noseweights.
Battery level - if I was going off grid regularly I'd fit an in-line digital readout for a few pounds
Gas - my bottle has a gauge that although not perfect gives a guide and I carry a small Campingaz back up that is also used on the Cadac.
Pitching level - spirit level always kept in the door
Roof hatch and window - could be useful for the roof, but not sure it would work. The reports of loose pop-tops is usually [thank goodness] owners lowering them and driving offf without latching them down as opposed to driving off with them still up.
Temperature - if it's hot I open the window.

I don't wish to sound negative, but for me I don't think it is worth it.

Colin