The app is free in the Oculus Store, and don't be dissuaded by the Korean-only product page -- it supports English.

Yes, it would be awkward and impractical to walk around wearing a VR headset (and your phone) at all times, so the current app is more for special situations. And Samsung knows it -- the Relumino team hopes to develop "glasses-like" hardware that achieves similar results without drawing attention to wearers or adding too much bulk. Even in its current state, though, this could be valuable for any visually impaired person who'd like to supplement their eyesight without springing for expensive specialized equipment.