When the group gets spread out on the trail, staying in touch gets hard
On longer hikes, groups often spread out or split up at rest points. With no cell signal in the mountains, staying in touch when someone falls behind can be a real problem. denntatsu connects hikers' phones directly, with no server involved, using devices you already carry.
What you can do with denntatsu
Join a channel in seconds
Scan a QR code to connect offline. No server needed, works off-grid.
Push-to-talk, like a walkie-talkie
Hold the button to talk, release to listen — just like a walkie-talkie, with nearby hikers.
Voice and text, both ways to reach the group
Text chat works alongside voice — useful for coordinating meetup points and breaks.
How it works
- 1
Connect at the trailhead
Before you set off, scan the host's QR code to join the channel.
- 2
Talk at the press of a button on the trail
Just press and talk to share rest points or call out when the group splits up.
Voice conversation is designed for nearby hikers in direct radio range. If you get too far apart, voice won't reach. Operate the screen only after you've stopped.
What to know before you use it
- Delivery is best-effort. Range depends on surrounding terrain, tree cover, and device hardware, and is not guaranteed.
- Only one person can talk at a time (half-duplex) — this is not an always-on, everyone-talks-at-once connection.
- Voice conversation is designed for close-range, tight-knit groups where hikers are in direct radio range of each other. A widely spread-out group is not guaranteed to stay connected.
- Text chat, like voice, only reaches devices you're directly connected to.
Frequently asked questions for hikers
How far does it reach?
Range depends on surrounding terrain, tree cover, and device hardware. Open ridgelines tend to reach farther, but no specific distance is guaranteed.
Is it free to use?
Yes, denntatsu is free to use. Normal-mode calls have a 30-minute session limit (removed with a day pass or monthly plan). The disaster SOS feature is entirely free and unlimited (SOS is not a substitute for official emergency calls, and delivery is not guaranteed).
Can I rely on this if I get into trouble on the mountain?
No. denntatsu is not a substitute for official mountain rescue services or emergency preparedness. Please continue filing a hiking plan and carrying other means of communication as you normally would. What denntatsu can do is connect nearby devices directly, with no server involved, even where there's no cell signal. It also has a free, unlimited disaster SOS feature, but delivery is never guaranteed.
Do we need dedicated radios to use it?
No — a smartphone is all you need to join. It also works alongside hikers who already carry radios.
Does it work on trails with no cell signal?
Yes. Because it connects devices directly with no server involved, nearby hikers can connect directly even where there's no cellular signal. Delivery is best-effort — range depends on surrounding terrain, tree cover, and device hardware.
Can we reconnect if the group gets spread out?
Voice conversation is designed for close-range, tight-knit groups in direct radio range — reaching a widely spread-out group is not guaranteed. Text chat likewise only reaches devices you're directly connected to.
Get Started
denntatsu is available now for Android. Download it free on Google Play to get started.
