I would really like to have an M5stack with e-paper display! I do have one of the use cases you mentioned - bitcoin price ticker, but I'm not using M5Stack due to several limitations, the biggest of which is that the display cannot stay ON while device is sleeping.
If anyone develops an M5stack with e-paper display (and eliminates the above limitation), I will gladly buy large quantities of this device!
Hey @ajb2k3, thanks for your input, but I'm afraid bigger/external battery doesn't answer OP's question and neither the issue I referenced. An e-paper display will certainly render the M5stack a lot more energy efficient while preserving the same product size (while external battery will just make the product bigger). And yes, e-papers of this size do exist, though are probably more expensive than the OLED.
@Mati if your M5stick is indeed in deep sleep while the display is on, then the issue I referenced earlier affects only the M5stack. I don't see why this issue is not fixed in this product...