MY PERSONAL OPINION.....Complete snake oil. Yes, a swamp cooler works but it lists the cooling power as 500W which is NOT a measure of cooling power. BTU's, that would be cooling power.
It also lists the cooling area as 10 square meters (90 SF) but with lighter and lighter rings (less and less cooling) for the majority of that space. If you use this in an air conditioned space to increase the cooling exactly where you are sitting (or doing Yoga) it should blow cool air in your face. Otherwise, it's not really going to do anything and I can't see any possibility that it would have any value in an RV situation.
The tiny water reservoir lasts 6-8 hours and then needs to be refilled. It says it works up to 70% humidity but if you have ever been in 70% humidity I can tell you that it won't do a thing to help cool you down unless the A/C is already running.
What I post is my 2 cents and nothing more. Please don't read anything into my post that's not there. If you disagree, that's OK.
Can't we all just get along?