Of course. Many sensors use I²C already, so it would be extremely easy to hook them up. So a sensor-loaded OH seems trivial. Barometer, colorimeter, temperature, humidity, hal-sensor, gyroscopes, magnetometers, sound decibel, lux, ultrasound distance meter, radar (Nokia was already toying with that concept), PIR sensor, 433MHz tranceivers for home domotica... You name it.

Also, put a CAN-transceiver in there and you can use the Jolla as extra console for your car, getting more, and more accurate readings from the car's sensors. Perhaps even tweak settings.

If the main display is OLED or something very akin, I can't see much need for an eInk display. I actually prefer to read books on the N9 at night than on my eInk e-reader...