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denntatsu

Connect, Even Offline.
denntatsu

Direct peer-to-peer communication without servers. Your go-to for outdoor adventures, with free unlimited disaster SOS and safety check-ins.

Works Offline
Get it on Google Play

Your New Outdoor Companion

Stay connected with teammates in remote areas—motorcycle touring, hiking, airsoft, anywhere without signal.

Home screen showing options to create a channel or join via QR code scan

Connect Instantly via QR

Scan a QR code to join offline. No servers. Works anywhere, even with no signal.

Call screen with PTT push button active

Push to Talk, Walkie-Talkie Style

Press and hold the PTT button to send. Supports hands-free auto send and receive.

Chat screen

Voice and Text Together

Send voice and text messages in parallel. Stay connected with your team in one app.

Get it on Google Play
TouringHikingAirsoft

When Infrastructure Fails, We Relay

When cell towers go down, nearby devices relay SOS and safety info peer-to-peer, spreading help across a mesh network.

SourceDestination

When one path breaks, another carries your message.

SOS broadcast screen with help needed status and liability notice

Send SOS Right Now

Broadcast your GPS location and situation with one tap. Disaster SOS is free and unlimited.

This app is not a substitute for emergency services (110, 119). Message delivery and latency are not guaranteed.
Disaster bulletin board showing safety and rescue posts

Share Status Locally

Post "I'm here," "I'm safe," or requests for help on a local shared bulletin board.

Disaster mode home screen with SOS send, bulletin board, and relay status options

Messages Keep Relaying

Undelivered messages stay in the network, relayed through multiple hops until they reach the recipient or expire.

This app is not a substitute for official emergency systems. Message delivery, latency, and reliability are not guaranteed and depend heavily on the actual radio environment, number of devices, and distance.
Get it on Google Play
Disaster SOS

Frequently Asked Questions

Does it really work with no cell signal?

Yes. denntatsu connects nearby devices directly (BLE control plane + Wi-Fi voice) with no server in between, so you can talk and chat even where there's no cellular reception.

Is the disaster SOS feature paid?

No. Disaster SOS and safety-sharing are entirely free and unlimited. Only the peacetime calling feature (30-minute session limit) is part of the paid plans.

What is it used for?

Outdoor activities with no cell signal — motorcycle touring, hiking, airsoft — and, during a disaster when cellular infrastructure is down, sending an SOS or sharing your safety status.

Which platforms are supported?

Android is available now — download it free on Google Play. iOS is planned for a future release.

Is message delivery guaranteed?

No. denntatsu is not a replacement for official emergency services (110/119 in Japan) and does not guarantee delivery. Actual reach depends on radio conditions, device density, and distance.

Is it hard to connect with others?

No. Just scan a QR code to connect offline — no server registration required.

How It Works