I’m Ilia, I build Callmar, a SIP client for iPhone. Not here to replace FreePBX — I run it against Asterisk/FreePBX myself.
The painful bit on iOS is still background: if you only REGISTER from the app, incoming dies when iOS suspends you. We added an optional push relay that forwards SIP signaling only (INVITE/etc.), never RTP. Audio stays phone ↔ your PBX/ITSP. Recording and transcription are off until the user consents; STT is on-device (Apple Speech on iOS 26+, WhisperKit optional). We don’t upload recordings to our servers.
If that’s useful to compare notes on: TLS/SRTP, multiple accounts, QR for provisioning, text-only CRM/webhooks. Happy to answer PJSIP endpoint settings that have bitten us (expires, contact rewrite, codecs).
App Store: Приложение «Callmar SIP клиент, ИИ анализ» — App Store
Site: https://callmar.online
If this belongs somewhere else, say so and I’ll move it.