The intercom moved into the smartphone — and it’s not magic, it’s SIP/VoIP
At PDP Mobile, we turned a phone into a digital intercom: a VoIP call over SIP through Asterisk, WebRTC for audio/video, CallKeep for the native incoming-call screen, and HLS camera streaming.
In PDP Mobile, we turned a phone into a full-fledged digital intercom. When someone rings the building entrance, the app accepts a VoIP call over SIP through Asterisk, and WebRTC provides audio/video without the usual “hello, can you hear me?” experience. For the native incoming-call screen, we connected CallKeep — everything looks like a regular call, without any hacks.
The fun part started not in the demo, but in real life: the internet blipped, the app went to the background, Wi‑Fi switched to LTE right in the elevator. We handled connection loss, background mode, and network switching so the intercom wouldn’t “drop” at the worst possible moment.
We also added HLS camera streaming: the resident sees who’s at the door first, and only then answers. In an era when everything is becoming smart, an intercom without video is almost retro 😅