Sony PRS-600. The resistive touchscreen does add a reflective layer, so yeah, current models are way better. But it's more than that. Before sleeping it's best to avoid (bright) light. Melatonin and such. The white-on-black text on N9 is perfect for that. Also, I can read comfortable laying on sides or belly, and don't need glasses as it is easier to keep the device close to one's eyes.

For the Jolla OH, an alternative for eInk would be Mirasol, made by... qualcomm. However, the I²C interface might be too slow for this.

Good point. I work in the mobile software development business. We now focus on BYOD and Android. But for some types of work a standard mobile phone won't suffice. Laser barcode scanners are way better in many ways than using the camera to scan 2D barcodes. For some tasks very accurate GPS (with things like WAAS) is needed. Currently this would require specialized and expensive devices, or stand alone. A OH-concept would make it easier to design and cheaper to produce.

Also, the new iPhone 5S has an M7 "motion" coprocessor or whatever it is called. Turns out this is a very low-power Cortex A3 CPU capable of continuously processing movements. The OH could provide the same functionality to the Jolla. I don't know if it is possible to communicate with the internal sensors from the OH (two bus masters on I²C?) so you wouldn't need an extra sensor in the OH. But the option of such coprocessor in the OH seems very well possible to me.