My new L3560 came with a Parallelogram mechanism from the bucket attachment to the loader arm where I can see it. one part lets me know when its level at ground level, one part lets me know (keep) it's level throughout the buckets travel from full down to full up.. on my pallet forks I made a swinging piece of flat steel that always hangs plumb, I look for the relation of this to the fork carriage frame to verify the forks position... since I trenched the yard unknowingly
I believe there is, I was asking about such a thing when I was shopping around for my tractor. It comes on the 3560, but something similar can be added to other models, I think it was around $50.