Mobile App Development for iOS, Android & .NET
I’m Justin Sinnard, a senior full-stack mobile developer specializing in iOS (SwiftUI), Android (Jetpack Compose), and .NET / Azure backends. I build custom apps for small businesses, creators, and startups that need real, production-ready software — not just a website.
Available for custom app projects and contract work. Remote or local (Wisconsin / Oshkosh area).
Featured Project: PumpPal
Cross-platform fitness app built with SwiftUI, Jetpack Compose, and a .NET backend on Azure. Includes plans, workouts, progress photos, measurements, subscriptions, and full error handling.
- iOS & Android native apps
- Secure authentication & token refresh
- Azure API + SQL database
- In-app purchases & ads
What I Do
Mobile App Development
Custom iOS and Android apps built with modern tech: SwiftUI and Jetpack Compose. Perfect for small businesses, gyms, creators, and startups that need more than a website.
Backend & APIs
.NET / C# APIs, Azure hosting, SQL databases, authentication systems, and background jobs. I design and build the backend that powers your app.
App Modernization & Fixes
Fix crashes, clean up legacy code, and convert old apps to modern frameworks (SwiftUI, Jetpack Compose). I also offer hourly consulting and feature development.
Looking for a Local App Developer?
If you’re searching for a mobile app developer near you in Wisconsin or the Oshkosh area, I build custom apps for small businesses: landscaping, fitness, retail, restaurants, and more.
Tell Me About Your Project