Halflight

Most hikers find out too late that the way back is longer than the way out. Halflight records your climb as you walk it, works out what the return leg will cost at your own measured pace, and counts down to the last minute you can still turn around and be off the mountain before the light goes.

It is not a daylight widget. It fits Tobler's hiking function to the pace you are actually walking today, adds the Naismith and Langmuir corrections for the descent, replays your own recorded profile in reverse, and computes civil dusk for your exact position. When the margin runs out it says TURN BACK, on the wrist, without a phone.

WHAT IT DOES

• Live turnaround time: the last minute you can keep going
• Your real pace versus Tobler, updated as you climb
• Return time from your own recorded ascent profile, in reverse
• Civil dusk or sunset as the target, computed on the watch
• Adjustable safety margin and an early warning with vibration
• A summary of distance, climb, descent and pace for the walk
• Five languages and a glance

WHAT IT NEEDS

• GPS. Everything is worked out on the watch: no phone, no account, no internet
• Halflight is a planning aid, not a substitute for a map, a headlamp and your own judgement