TrailMark: a trail display for the hike
An iPhone app and a 3D-printed handheld screen with miles, ETA, a route map and a parade of tiny hikers. Built in a week, then taken to Vermont.
I wanted hike stats I could see at a glance without pulling out my phone every few minutes. TrailMark is the result, in two parts:
- The iPhone app tracks the hike (route, miles, steps, ETA, moving time, climb and splits) and broadcasts it over Bluetooth.
- The display is an ESP32 “Cheap Yellow Display” in a 3D-printed case with its own battery. It has no sensors. Everything on the screen comes from the phone.
The screens
The display cycles through a dashboard, steps, miles (with an OFF ROUTE warning if GPS puts me more than 60 m off the trail), elapsed time, ETA, a live route map and a six-hour weather forecast. When I reach the day’s endpoint it flips to YOU MADE IT!
Between screens, a little pixel hiker walks across a forest backdrop, stops to wave, and walks off. Everyone on the trip got their own character, and so did the dog. Before the hike starts, the whole crew parades across the screen.
The trip video
At the end of the trip, the app turns the hike into a short video: the crew walks out, then the stats count up.
The build
Most of the work happened in a single week. The case went through several rounds: a new body to fit a flat 2000 mAh LiPo pouch, a bezel redesign, and figuring out the right M3 screw length so it would survive a backpack. Battery handling took a surprising number of firmware versions: detecting the charger, reading 100% after unplugging, and sleeping safely when it’s empty.
Then it came with us to Vermont.
