I think the best point of this is that because of the reverse charging from the phone1 it could power an external case with completely different lights, LCD (let your imagination run wild here) etc.
One idea just crossed my mind - what about some custom lights patterns unlocked or other form of interaction when two nothing phones meet i.e. are close to each other?
Great thoughts _ukaszFerenc, nice to hear from you.
Without revealing too much, our mission is pretty much aligned with your suggestion of ...
_ukaszFerenc