Five hikers, all blind or partially sighted, crossed a mountain range in eastern France recently thanks to an innovative GPS system that developers hope can help millions of people with vision problems.

Armed only with their white canes and the experimental smartphone app - unaccompanied by sighted guides - the group trekked 80 kilometers in six days through fields and forests in the Vosges range near the German border.

Worn in a small pouch over the stomach, the Navi'Rando - named after "randonner", the French word for hiking - warned of bends in the path and turning points at regular intervals.