Hire Swift & Kotlin Developers
Native iOS & Android • CallKit • VoIP SIP • PJSIP
Dedicated Swift and Kotlin engineers with deep VoIP expertise — CallKit, ConnectionService, PJSIP, and SRTP encryption. Ship App Store–compliant calling apps that perform at carrier quality.
Quick answer
How do I hire a Swift and Kotlin developer?
Share your requirements with CelloIP and get matched Swift and Kotlin developer profiles within 1–2 days. Interview them, and your developer can start within a week under an NDA, with full IP ownership and a 30-day money-back guarantee. Every developer has 3+ years of hands-on experience, backed by CelloIP's 9+ years in VoIP and real-time communication.
Developer Roles & Rates
Transparent pricing. No hidden fees. Scale up or down monthly.
Senior iOS Swift Developer (VoIP)
Custom quoteNative iOS VoIP expert with App Store submission and CallKit compliance experience
Swift 5, CallKit, PushKit, PJSIP, linphone SDK, AVAudioEngine, CoreTelephony, SRTP
Senior Android Kotlin Developer (VoIP)
Custom quoteNative Android calling specialist with Telecom framework and background service expertise
Kotlin, ConnectionService, FCM, PJSIP-Android, AudioManager, Bluetooth SCO, WebRTC-Android
iOS/Android Dual-Platform Developer
Custom quoteFull-stack native mobile developer delivering both iOS and Android simultaneously
Swift + Kotlin, shared SIP logic, native SDK bridging, Xcode + Android Studio, CI/CD fastlane
SwiftUI / Jetpack Compose UI Developer
Custom quoteModern declarative UI specialist for polished, App Store–ready interfaces
SwiftUI, Jetpack Compose, Figma-to-native, accessibility, dark mode, WCAG compliance
Technology Stack
Full-spectrum native mobile expertise — from PJSIP SIP stack to App Store submission.
iOS (Swift)
Android (Kotlin)
SIP & Media
Backend Integration
DevOps & Release
Architecture
Apps We Build
Native iOS and Android apps built for real-world calling performance.
White-Label SIP Softphone
Fully branded iOS and Android dialer with HD voice, SRTP encryption, and multi-account SIP support
Healthcare Mobile Telemedicine
Secure calling app with CallKit integration and encrypted patient communication
Enterprise Mobile PBX Client
Native mobile extension for FreePBX/FusionPBX with presence, BLF, call transfer, and conference
Contact Centre Agent App
iOS/Android agent interface with ACD queue integration, click-to-call CRM dialling, and real-time analytics
Real Estate Click-to-Call App
Instant property inquiry calling with CRM logging, callback scheduling, and lead routing
Field Service Communication App
PTT + VoIP hybrid app for field teams with GPS tracking, offline messaging, and group calls
CelloIP vs. Generic Agencies
Why VoIP-specialised native developers outperform generalist shops.
Engagement Models
Dedicated Developer
One full-time Swift or Kotlin developer embedded in your team. Full IP ownership, NDA from day one.
Custom quoteiOS + Android Team
Parallel iOS and Android development with shared SIP logic. Faster delivery with native quality on both platforms.
combinedSprint / Fixed Scope
Defined deliverable with milestone billing — ideal for MVP dialers, app audits, or feature sprints.
Fixed-price quoteFrequently Asked Questions
Can you develop both iOS and Android simultaneously?
Yes. Our dual-platform developers work in parallel with shared SIP business logic (via a Kotlin Multiplatform or shared C++ PJSIP layer) and platform-native UI layers. This reduces duplication without sacrificing native quality.
Do your apps pass App Store and Google Play review?
Yes. We follow Apple's VoIP entitlement guidelines (PushKit + CallKit) and Google Play's background process policies. Our developers have shipped multiple VoIP apps through both stores and handle the review process end-to-end.
What SIP libraries do you use on iOS and Android?
We primarily use PJSIP 2.x (cross-platform, compiled for iOS and Android) and linphone SDK for clients requiring a proven commercial-grade SIP stack. For WebRTC-only projects, we integrate Google's native WebRTC iOS/Android libraries directly.
How quickly can a developer start?
Typical onboarding is within a week after NDA signing and requirement handoff. We keep a bench of pre-vetted Swift and Kotlin VoIP developers ready to start immediately.
"The Swift developer from CelloIP got our CallKit integration right on the first attempt — background VoIP push, native call screen, proper audio session management. It would have taken our team weeks to figure out. Shipped to App Store in under 30 days."
Ready to Ship Your Native iOS & Android VoIP App?
Share your requirements. We'll match you with the right Swift or Kotlin developer within 1–2 days — NDA signed before the first call.