Case Study - A Lightweight iOS Speedometer with Premium Features

Overview

Speedometer is a native iOS application that provides real-time GPS speed readings with a focus on simplicity, privacy, and accessibility. The app was designed to do one thing exceptionally well: show your current speed in a clean, readable format.

In a market full of bloated speedometer apps with unnecessary features and intrusive ads, we wanted to create something different—a lightweight utility that respects user privacy and provides genuine value through thoughtful premium features.

Design Philosophy

Privacy First

Location data never leaves the device. We don't collect analytics, track users, or share any data. The app simply reads GPS speed and displays it—nothing more.

Accessibility First

VoiceOver support was built into the architecture from day one, not bolted on later. All speed units have descriptive accessibility labels, and the interface scales properly with Dynamic Type.

Performance First

At under 400KB compressed, the app installs almost instantly. No heavy frameworks, no unnecessary dependencies—just native Swift and SwiftUI doing what they do best.

Key Features

Free Features

Real-Time Speed Display

The main interface features a large, prominent speed reading using a 140pt thin-weight font. Numbers use monospaced digits for stable alignment as values change, with smooth animated transitions between updates.

Multiple Speed Units

Users can switch between five measurement units: MPH, KM/H, M/S, Knots, and Feet per Second. Preferences persist between sessions, and conversions happen in real-time as the unit is changed.

Smart Formatting

Speeds below 10 show one decimal place for precision (e.g., "5.2 mph"), while higher speeds display as whole numbers to reduce visual noise.

Premium Features

The freemium model offers genuine value for power users:

Speed Alerts

Set a configurable speed threshold and receive haptic feedback when exceeding it—perfect for staying within speed limits. A 2-second cooldown prevents alert spam during fluctuating speeds.

HUD Mode

Mirror the display for windshield reflection mounting, transforming the phone into a heads-up display.

Premium Colour Themes

Six carefully designed themes: Midnight (cool blues), Sunset (warm oranges), Ocean (cyan tones), Neon (electric green), and Retrowave (magenta with cyan accents), plus the default light theme.

Keep Screen On

Prevent display auto-dimming during use—essential for automotive applications.

Technical Implementation

Architecture

The app uses SwiftUI throughout with an MVVM architecture. Key services are implemented as ObservableObjects with published properties for reactive UI updates:

• LocationManager — Handles GPS authorisation and continuous location updates
• PurchaseManager — Manages StoreKit 2 transactions with async/await
• SpeedAlertManager — Coordinates threshold monitoring and haptic feedback

StoreKit 2 Integration

We implemented Apple's modern StoreKit 2 framework for in-app purchases:

• Async/await patterns for clean, readable purchase flows
• Cryptographic transaction verification for security
• Automatic entitlement checking on app launch
• Background transaction listening for restored purchases

The purchase is a one-time unlock, not a subscription—simpler for users and appropriate for this type of utility app.

GPS Configuration

CoreLocation is configured for automotive navigation with best accuracy settings. The app handles all authorisation states gracefully, providing clear messaging and direct links to Settings when permissions are denied.

Quality Assurance

The codebase includes comprehensive unit tests covering:

• Speed conversion accuracy for all five units
• Edge cases like zero speed and high-speed scenarios
• Real-world speed validation (walking, city driving, motorway)
• Formatting logic for decimal place handling

What we did