Turnaround: an open‑source hiking buddy that knows when you should turn back, and tells someone if you don’t come home

Description and use

Turnaround is a local app that predicts hike finish time, gives an audible briefing, starts a reliable timer, and automatically notifies contacts if the hike is overdue.

Problem

Hikers often over‑estimate how long a trail will take and fail to notify trusted contacts if they don’t return on time.

Outcome

Turnaround delivers a personalized hike‑time estimate, an audible briefing, a crash‑resistant safety timer, and automatic emergency notifications, improving safety for solo hikers.

Workflow

• 1. Enter trail distance, elevation gain and trailhead into the app. 2. Turnaround predicts a 90 % finish time, a "turn‑around by" time, and a "back‑by" time. 3. The app speaks a briefing using Gemma 4 and Kokoro. 4. The hiker taps "Start" to arm the safety timer. 5. The hiker checks in on the phone. 6. If the hiker misses the check‑in past the alert deadline, an email is sent to the emergency contact. 7. If the hiker checks in after the alert, a second email is sent confirming safety.

Evidence

I held out 1,438 hikes the model never saw and compared it with Naismith: Average error 44.1 min vs 34.8 min; Real times inside the predicted 90% band 89.5%

Source

The safety timer is a Temporal workflow. One tripWorkflow per hike races a check‑in signal against a durable timer set to the alert moment.

Source

If the hiker misses the check‑in while the mail server failed, activity retried; alert went out on attempt 2.

Source