I had Big Foot Levelers on a class "C" a few years ago. They worked quite well. They are also a little easier for after-market install since each leveler leg has it's own pump so you don't have to run hydraulic lines. One caution - they use the pump to retract (no springs) - the pumps make a rather loud high pitched noise. If you're trying to make a quiet early morning getaway, when you hit the "All Up" button and lite off all 4 pumps it's not gonna be a quiet getaway.
That was about 6 years ago, so they may have changed by now. Just be sure to ask, if you consider using them. Except for the noise, I thought it was a very good system, fully automatic leveling and probably a lot less than HWH.