A cryptocurrency backed by entropy.
CMB could do it now, if it were hooked up with random.org. The idea being that making purely random numbers, outside of hardware is hard.
Ignoring security concerns in acquring said entropy, just the idea of backing a currency with them, much like you could back a currency with gold, seems to have some merit.
Why would you do this?
Because entropy is *always* going to be valuable, so long as there are computer systems, being able to make a system call to get a random number is going to be a VERY handy thing. Even more universally handy than use of a cryptocurrency system in general because use of a cryptocurrency probably needs random numbers. It's the one thing, other than XRP, that you could probably base a cryptocurrency on.
Because entropy is generated more or less constantly, but there are swings in supply and demand. Having a stable currency with a supply would allow supply and demand to work more smoothly, with exchanges set up via the same means we have set up exchanges for xrp/btc, the same tools would suddenly work to establish steady streams of entropy.
Way to turn one of the universe's most abundant natural resource into a revenue stream, eh?