Service · Flutter calling apps
One Dart codebase. Two native calling apps. Built on a proven, open-source SIP core.
We build audio and video calling apps in Flutter, backed by an open-source SIP SDK — a production-grade SIP/media engine already proven on iOS and Android — so you get one engineering team and one codebase, not two apps drifting apart.
Why one codebase
Built on an open-source SIP SDK.
One Dart codebase gives you one engineering team and one release cadence, instead of an iOS app and an Android app that quietly drift apart. Calling, video and encryption run on a proven, open-source SIP SDK — already used in production on both platforms.
Ringing never waits on the app
An incoming call rings through the OS's own call screen — CallKit on iOS, Telecom on Android — even if the app was fully closed. Nobody misses a call because the app hadn't launched yet.
Video that scales to a grid
Multi-participant video, picture-in-picture and on-screen overlays all behave like ordinary parts of the layout — nothing fights for its own window.
A proven SIP core, not a rewrite
Signalling, NAT traversal, codecs and encryption run on a proven, open-source SIP SDK — the same engine already used in production on both platforms.
What's built and working
Calling, encryption and diagnostics — verified end to end.
Audio and video calling, place and receive, both directions. Multi-account sign-in with an account switcher. In-call mute, speaker, camera toggle and DTMF dial pad. Live call history with per-entry and bulk delete.
SRTP, ZRTP and DTLS-SRTP, including Post-Quantum ZRTP key agreement — labelled as such rather than a blanket "end-to-end," because that's the honest claim. ZRTP's short authentication string is available to read aloud and verify.
Round-trip time, jitter, packet loss, audio/video bitrate up and down, ICE connection path, and the negotiated codec — read straight from the running call, not estimated.
Adaptive rate control, echo cancellation, video FEC, IPv6, Wi-Fi-only mode, auto-answer with a configurable delay, and proximity-sensor screen blanking.
Remote provisioning URI support, so an IT team can roll the app out pre-configured against their own SIP PBX rather than asking every user to enter settings by hand.
Light, dark or system theme, seeded from a single brand accent colour — the whole app re-themes from one value, which is what a white-label rollout needs.
This is a real, working codebase, not a concept — sign-in, multi-account switching, call history, contacts, settings, and two-way audio/video calling have all been verified running on both platforms.
Need a calling app that doesn't fork into two teams?
Tell us the SIP provider or PBX you're already on — we'll tell you what a Flutter build looks like against it.
Email info@neithsystems.com