The lock screen wallpaper of his iPhone (a 4S) was clearly a satellite photograph of some kind. Overlaid upon it was the angular, semi-transparent blue track line of a Google Maps-style route. Some operating systems enable mapping on the lock screen at the platform level – Windows Phone offers this on certain devices, for instance – but Apple’s tightly controlled UX does not.

My interest was piqued – how had the map become his unlock screen? Upon further enquiry, it transpired the map showed a walking route he’d taken recently with his dog. The route was planned at home on a Samsung Galaxy tablet, using an Android app capable of showing Ordnance Survey’s detailed, walker-friendly maps of the UK. Once the waypoints had been laid out, he’d overlaid it with the satellite image.

The tablet, however, was something which lived exclusively in the home: too big and fragile to be carried on a walk. The iPhone (his personal mobile, alongside a Samsung Galaxy S3 provided by work) was his chosen walking companion, so he’d taken it from his pocket, photographed the screen of the tablet and then set the image as the iPhone lock screen.

In his mind, it was a backup. He knew the territory relatively well already. Indeed, the friend who’d joined him on the walk was surprised he’d even bothered to carry a map, and they hadn’t strayed far from marked routes in a rural area where the nearest road would never have been more than half a mile away. However, there was something about the at-a-glance convenience of the lock screen which made it a reassuring reference point.

Mapping, of course, is core the contemporary mobile user experience. We’ve had several fascinating talks on its intricacies at recent MEX, from Peter Skillman (then head of design at HERE, the Nokia-owned mapping subsidiary recently acquired by a consortium of car manufacturers) to Ben Scott-Robinson, head of interactive experience at Ordnance Survey. However, even with all the resources invested in understanding users’ relationship with location awareness, I wonder how many design teams could anticipate a situation where Android tablet and iOS phone were used in such a combination, with the simple act of taking a digital photograph as the linkage between them?

It reminded me of Yota, one of the few Android manufacturers attempting to provide a distinctive hardware experience. The YotaPhone products feature a traditional colour touchscreen on one side and a touch-enabled, black and white e-ink display on the other. Yota’s software customisations allow users to mirror anything seen on the main colour display to the e-ink panel on the rear of the device. There the image can live in low power mode for days, allowing users to store useful reference items, like maps, and view them without the usual battery drain associated with mapping apps.