Ok, I've had the free trial for a week now, and I feel I can safely say that Endel isn't some algorithmic genius, it's simply a pleasing ambient album. For example, there are two distinct tracks on the sleep channel, and that's it, no matter if sometimes a somewhat ancillary ticking clock is playing instead of a white noise filter sweep mimicking the ocean.
There's no shame at all in making a good ambient album. They've done that. But the description of Endel is truly misleading and tries to represent Endel as something more. And on top of that, it charges an ongoing subscription fee that is not equivalent to the market price of an album, which, again, is what this is. Sorry, but I'm not gonna subscribe and have to renew $25 every year for the latest Carly Rae Jepsen album either. The lack of promise of future updates/material, on top of it all, makes this whole enterprise seem very dishonest. Pretty good album, though.
For something truly ambitious and algorithmic, see Brian Eno's Scape app for iPad. Relatively expensive for an iPad app, but a one-time purchase and filled with at least 10x the material of Endel.