App: OtoSignal OtoMoji Hz / Last updated: October 11, 2026
This app (the "App") respects your privacy and works to protect personal information. This policy explains what information the App handles and how it is used.
1. Personal information collected by the developer
We (HacTools) do not collect, store, or send the text you type, send, or receive in the App, your name, your passphrase, microphone audio, or the read-aloud voice. The App has no developer server.
However, for the ads shown in the App, Google AdMob collects information from your device and sends it to Google. The types of information are listed in "9. Ads".
Also, if you send a report email, we receive that email (including your email address). See "4. Reporting".
2. Information stored on your device
Settings (pitch, volume, speed, volume of received voice, name tag, "Mosquito, Go Away" duration, language, etc.), voice settings (voice type, voice pitch, reading speed, your own voice, sending pitch), your name, your passphrase, the last message you sent, quick phrases (including the ones you add), and the result of "Check what this phone can play" are stored only on your device. The passphrase is stored on the device as plain text and is never sent out.
They are never sent to the developer's or any third party's servers.
Messages you receive are not saved. They disappear when you quit the App (they stay on screen while the App is open).
This information is lost when you uninstall the App or clear its data. It is not carried over by device backups or when you change devices.
If you clear the name or passphrase field and tap "Use these", the saved value is cleared too.
3. Messages and your name
The App turns your message into a sound signal and plays it from the phone's speaker. It does not use the internet.
Any nearby phone running an app with the same mechanism within range of the sound can pick it up and turn it back into text. Without a passphrase, anyone nearby can read both your name and your message.
If you enter a name, your name is sent along with your message.
4. Reporting
If you press and hold a message you received and choose "⚑ Report", your device's email app opens with an email to the operator ([email protected]) containing the message, how the sender was shown (name and time), the date and time, and the app version.
You decide whether to send it. The App never sends it automatically. The email is sent from your own email app and account.
Emails we receive are used only to handle the report.
5. Passphrase (encryption)
When you enter a passphrase, the App creates a key from it on your device (PBKDF2) and encrypts your message and name (AES-GCM) before turning them into sound. Only phones with the same passphrase can turn it back into text.
The passphrase itself is never sent. The only things outside the encryption are a 1-byte marker that tells which passphrase is used, and, when you send at a custom pitch, a name tag that contains only the pitch number.
When you send by voice, the voice itself is not encrypted (it is sent as sound). A passphrase only hides messages sent as text.
6. Microphone
The microphone is used to pick up the sounds played by the other phone and turn them back into text or voice.
"Check what this phone can play" plays short tones from your speaker and measures how loudly your own microphone picks them up (about 8 seconds in total). Only the number of how many kHz your phone could play is kept.
The audio is only processed on the device, on the spot. Nothing is recorded, saved, or sent.
The microphone is used only from when you start receiving until you stop, and while checking the pitch range. When you stop receiving, the microphone stops too.
Before the microphone is used, the App explains the purpose on screen, then shows the device's permission request. Without microphone permission, you can still send text or voice, use quick phrases, and use "Mosquito, Go Away" (but you cannot receive).
7. Read-aloud voice (sending by voice)
For the read-aloud voice, the App uses your device's text-to-speech (Android TextToSpeech). The voice is first written to a file on the device, then shifted in pitch and sent as sound.
The App never sends your text anywhere (it only reaches nearby phones as sound).
The text-to-speech feature itself is provided by the device's provider (such as Google), and how it handles information follows that provider's policy.
8. Device permissions
Microphone: as described in 6.
Internet: used to show ads. The fonts are built into the App and are not loaded from the internet. Sending and receiving messages or voice does not use the internet (it works directly by sound).
Change audio settings: used to set how the phone plays and picks up sound.
Advertising ID: used to deliver ads (as described in 9). The ad component (Google Mobile Ads SDK) also uses permissions such as checking the network state.
The App does not use permissions such as location, contacts, photos and files, camera, or phone.
9. Ads (use of data by a third party)
The App shows ads using Google AdMob, a mobile advertising service provided by Google. For ad delivery, measurement, and fraud prevention, AdMob collects the following information from your device and sends it to Google.
Device or other IDs — Advertising ID, App Set ID
Approximate location — IP address (used to estimate your approximate area, at about the city level)
App activity — number of interactions such as app launches and taps
App info and performance — diagnostics such as launch time and hang rate
This information is handled under Google's privacy policy, and it is sent encrypted with TLS. The App has no in-app purchases, such as paying to remove ads.
The App shows a single banner at the very bottom of the screen. It is hidden while you are typing. Full-screen ads are not used.