I will develop softphone app, linphone app, esim app, esim website, voip app

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callum_fosterr
C
callum_fosterr
Callum
develop softphone app, linphone app, esim app, esim website, voip app
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develop softphone app, linphone app, esim app, esim website, voip app

About this gig

Need a carrier-grade communication solution? Whether you're launching a global eSIM marketplace, building a custom softphone, or fixing complex SIP issues, you need someone who understands telecom at scale.

What I Do:

I provide end-to-end development and expert troubleshooting for modern communication platforms:

Custom Softphone & Linphone apps with tailored UI/UX, SIP integration, and push notifications (FCM/APNs) across iOS, Android, and Desktop

eSIM ecosystems including SM-DP+ integration, GSMA-compliant provisioning, web platforms, and mobile apps

AI-powered VoIP with real-time transcription, sentiment analysis, and intelligent IVR agents

WebRTC solutions for browser-based calling and CRM integrations

Advanced VoIP debugging: one-way audio, NAT traversal, SIP ALG, jitter, and latency issues

️ Technical Expertise:

Protocols: SIP, WebRTC, RTP/RTCP, SRTP, TLS

Infrastructure: FreeSWITCH, Asterisk, Kamailio, OpenSIPS

Development: Flutter, React Native, C++, Python

I build secure, scalable, 5G-ready systems with clean architecture and reliable performance.

Lets discuss your project and bring it to life.

  • App type

    • Hybrid

  • Programming language

    • Dart
    • Java
    • Kotlin
    • Objective-C
    • Python
    • Swift
    • TypeScript
    • React Native
    • Flutter

  • Frameworks

    • Flutter
    • Ionic
    • NativeScript
    • Laravel
    • SwiftUI
    • Node.js
    • React Native

  • Purpose

    • Chat
    • Streaming
    • Booking
    • Social networking
    • Maps & navigation
    • Education
    • Productivity tools
    • Custom
    • Ecommerce
    • VPN

  • Tools

    • Expo
    • Xcode
    • Firebase
    • BuildFire
    • Visual Studio Code
    • Visual Studio
    • Supabase

  • Expertise

    • Cross browser/Device compatibility
    • Performance
    • Security
    • Design
    • Firebase
    • API integration

Get to know Callum

Callum

AI Powered Mobile App Developer Android and iOS Expert 8 plus Years Experience

  • FromCroatia
  • Member sinceApr 2026

  • Languages

    English, Spanish, French, Dutch
Welcome to my profile! I’m Callum Foster, a mobile app developer with over 8 years of experience creating high-performing apps for Android and iOS. I focus on building intelligent solutions by integrating AI features such as chatbots, automation, and data-driven functionality. From concept to launch—and ongoing support—I provide complete end-to-end development services. Let’s bring your idea to life with a powerful, user-friendly app. 📥 Reach out to get started!

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