It sounds like a traditional water heater would be fine for your application.
If you're looking for on-demand hot water without any wait at all - you could consider a tankless water heater. I got a Girard unit off eBay for my Scamp
13'. Hot water flows after a 10 seconds and you don't have to tow around 10 gal of dead weight
However I must admit the technology has limitations especially in consistent temperature control - it's fiddly and you have to be forgiving. So I can only suggest that you find a demo unit at a vendor or RV show and judge for yourself.