Off-topic, but vaguely related to Jolla's OH concept, so there is a tenuous link at least...
http://www.engadget.com/2013/10/29/m...ar-smartphone/
I vaguely recall someone going into lots of technical detail in order to poo-poo the Phonebloks concept.
Seems Google(Motorola) doesn't necessarily think it's infeasible, whether it'll result in real product one day remains to be seen ofc.