Right, this one has a hip strap, like a belt, and a thigh strap. The one I've seen uses two thigh straps, so just two around the leg, instead of one around the waist.
I have a fanny pack/ bum bag that I use for surfing. Having an extra strap to hold it flat on my thigh would be super useful, but it has to be watertight.
Edit: for anyone confused, yes, those two terms refer to the same thing, we just call it a different thing depending on which side of the pond you're on. As I understand it, fanny refers to something quite different in the UK.