Service · Mobile + custom application development

Custom mobile app development.

Cross-platform mobile and web applications tailored to your business goals. iOS, Android, and hybrid builds with intuitive UI/UX, robust functionality, and consistent performance across every device. Award-winning team, 14+ years, 500+ apps shipped.

Our expertise

Cross-platform mobile and web, with depth.

Tailor-made mobile and web applications that match your business goals. We prioritize intuitive UI/UX, robust functionality, and seamless performance across all devices, enabling you to engage users effectively across iOS, Android, and the web.

Native iOS

Swift, SwiftUI, and platform-native frameworks.

iOS-first builds when iPhone or iPad is the primary device. Apple Watch and tvOS extensions when the engagement calls for them. Direct access to platform features without abstraction layers.

Native Android

Kotlin, Jetpack Compose, modern Android tooling.

Android-first builds for Android-heavy markets or device-specific use cases. Material Design 3 by default. Wear OS and Android Auto extensions when needed.

Cross-platform

React Native and Flutter for shared codebases.

One codebase, two platforms when the use case justifies it. Cost-efficient when feature parity matters more than platform-specific polish.

Hybrid + web apps

Progressive web apps and hybrid mobile builds.

PWAs that install on iOS and Android without app-store gates. Hybrid builds for content-heavy use cases where web technologies fit better than native code.

Capabilities

From research to release, one team.

The same senior staff that scopes the engagement is the staff that builds, tests, and ships it. No bait-and-switch. No rotational handoffs at handover.

User research & UX

Research, wireframes, prototypes, polished UI.

User interviews, competitive analysis, information architecture, and high-fidelity Figma prototypes. Accessibility-first practice, WCAG 2.2 AA + Section 508 conformant.

Backend & APIs

Custom backends, REST and GraphQL APIs.

Node, Python, PHP, or Go backends as your stack requires. Strongly typed API contracts, OpenAPI documentation, and integration with the third-party services your app depends on.

AI integration

AI features built into the app, not bolted on.

Knowledge-base-grounded chatbots, recommendation engines, content generation, and predictive analytics. Cost-monitored production deployments, not demo-quality.

QA & release

Automated testing, app-store delivery, ongoing support.

Unit, integration, and end-to-end tests in CI. App Store and Google Play submission management. Crash reporting and performance monitoring after launch.

The integration layer

Mobile Backend, APIs & Third-Party Integrations

The backend is what allows a mobile app to do real work. OST builds mobile backends that support secure logins, user accounts, data storage, business rules, payment processing, reporting, notifications, and admin controls. As a custom mobile app development agency, we connect apps with the systems your business already uses, including CRMs, ERPs, eCommerce platforms, booking tools, analytics platforms, payment gateways, and custom databases.

For companies looking for a cross platform mobile app development company, this integration layer is often the difference between a simple app and a useful business platform. Our team works with REST APIs, GraphQL, SDKs, cloud services, and third-party tools to keep data moving securely between your app, backend systems, and business workflows.

How we work

Four phases. Same team across all four.

The phases that apply to every engagement, not just custom mobile app development. The team that scopes does the building, and the operating.

Phase 01 · 2–4 weeks

Discovery and scope.

Stakeholder interviews, technical review of existing systems, risk register, written scope with milestones and exit criteria.
Phase 02 · 3–12 months

Build and iterate.

Two-week sprints with working demos. Senior leads on every sprint review. Code reviewed, accessibility checked.
Phase 03 · 2–6 weeks

Cutover and stabilization.

Parallel run with rollback path. On-call coverage during the launch window. Stabilization continues until incident rate trends to zero.
Phase 04 · ongoing

Operate and evolve.

Multi-year retainer with the same team that built the product. Monthly check-ins, quarterly business reviews.

Read the full engagement model on the How We Work page.

Industries we serve

Custom Mobile App Development across 15 verticals.

Six core verticals where OST has the deepest engagement experience. Plus nine adjacent industries served on selective engagements.

Education & Public Sector

K-12 districts, charter networks, higher ed, and SLED. Multi-tenant CMS, accessibility audits, alumni directories, and FERPA-aware platforms.

Nonprofit & Civic

Mission-driven organizations and civic platforms. Donor systems, membership platforms, AI-powered outreach, and grant compliance reporting.

Healthcare & Wellness

Specialty practices, diagnostic labs, wellness brands, and clinical directories. HIPAA-aware engineering scoped per engagement.

Real Estate Technology

Commercial real estate, multi-tenant SaaS, brokerages, and self-storage. Built for scale, listing-feed integrations, and Fair Housing accessibility.

E-commerce & Marketplaces

OST's largest vertical: 29+ active retailers. Custom OpenCart, custom payments, multi-channel inventory, and ADA-aware checkouts.

Manufacturing, Industrial & B2B

B2B platforms, ERP integration, offline-capable field tools, and custom industrial software. Built for the operations teams that run physical-world businesses.

Also serves on selective engagements

Mobile App Modernization and Rebuilds

Older mobile apps can become slow, difficult to maintain, or limited by outdated technology. OST helps businesses modernize existing apps by improving performance, updating UI/UX, fixing code issues, upgrading frameworks, and rebuilding features that no longer support business needs. For companies looking for a custom mobile app development agency, the work starts with a full technical review of the current app, backend, APIs, database, security setup, and user experience.

From there, we recommend whether the app should be improved in phases or rebuilt on a stronger foundation. Android apps may need updates for newer devices, OS versions, Google Play requirements, integrations, and performance standards. As a custom android app development company, OST helps make those updates without disrupting the core business workflow.

We also support iPhone and iPad app improvements, including App Store compatibility, performance optimization, interface cleanup, and feature upgrades. Our custom ios app development services help businesses extend the life of existing apps while preparing them for future growth.

App Store Launch and Launch Support

Launching a mobile app requires more than uploading it to Google Play or the App Store. OpenSource Technologies (OST) supports the full release process, including build preparation, store listing guidance, testing, submission support, version control, and launch checks.

For Android-focused products, our experience as a custom android app development company helps businesses prepare apps for Google Play submission, compatibility checks, device testing, and ongoing updates. After launch, OST can support bug fixes, crash monitoring, OS compatibility updates, performance improvements, feature enhancements, and long-term roadmap planning.

The custom ios app development services include support for App Store requirements, performance review, device testing, and release preparation. This keeps your app reliable, secure, and useful as users, devices, and business needs continue to change.

Frequently asked questions

Common questions on custom mobile app development engagements.

How long does a typical custom app engagement take?

3 to 12 months from kickoff to first production release, depending on complexity. Pilot and MVP scopes can ship in 8 to 12 weeks. Enterprise builds with deep integrations run 9 to 14 months.

What does a custom app engagement cost?

Pilot scope (one platform, basic backend) starts around $40K. Production scope (multi-platform, custom integrations) lands $100K to $250K. Enterprise scope with deep integrations runs higher. Use our modernization cost calculator for a defensible bracket at our blended rate.

Native or cross-platform — which is right for me?

Native if you need maximum platform polish, deep integration with platform features, or you have a single dominant platform. Cross-platform when feature parity across iOS and Android matters more than platform-specific behaviors. We help you decide in discovery.

Will the same team stay on after launch?

Yes. Our default is multi-year retainer with the same senior staff. The senior on your kickoff call is the senior on year-five releases.

Do you handle App Store and Google Play submissions?

Yes. Submission management, store-listing copy, asset preparation, and policy-compliance review. We sit through the rejections and resubmissions so you do not have to.

What about accessibility?

WCAG 2.2 AA + Section 508 conformance is included in baseline scope, not an upcharge. Audit-ready documentation produced as part of every engagement.

Ready to build?

Pick a path forward.

Multiple ways to start: schedule a discovery call, run our cost calculator for a budget bracket, or use the contact form for a written response.