Case study · Side project
RallyRec
A rally reconnaissance app used by professional pilots and copilots to measure distances between corners. RallyRec combines GPS distance tracking with a Bluetooth button on the steering wheel, so the co-driver can reset the partial counter without letting go of the wheel.
GPS + BT
Core of the product
Pro use
Built for rally crews
Product
RallyRec is a distance-logging tool built for professional rally reconnaissance. Co-designed with French rally co-driver Olivier Brouze, creator and daily user of the system, it combines precise GPS measurement with a Bluetooth button mounted on the steering wheel, letting copilots reset distances between corners without touching their phone.
My role
- • Implemented the iOS app from a functional & visual spec
- • Built the GPS distance tracking using Apple’s location APIs
- • Integrated the Flic Bluetooth button for one-tap reset
- • Ran field tests and tuned behaviour based on real driving
Context
- • Side project built mainly in 2018 over a few weekends
- • Created with a French professional co-driver as domain expert
- • iOS first; Android developed separately by another team
- • Still in use today by rally pilots and copilots
How RallyRec works
A simple loop for reconnaissance: drive, reset between corners, and keep distances aligned with your notes.
Start the stage
The crew starts RallyRec before reconnaissance. The app begins tracking distance via GPS and displays both total and partial distance in large, readable digits.
Reset between corners
A Flic Bluetooth button mounted near the steering wheel lets the co-driver reset the partial distance with a thumb press, without reaching for the phone or taking hands off the wheel.
Use distances for pacenotes
During recce, the co-driver writes notes and simply glances at RallyRec for precise distances between corners. Distances stay consistent across passes, reducing guesswork and mental load.
Context
The opportunity
In rally, good pacenotes depend on precise distances between corners. Many crews still rely on tripmasters, manual resets or less specialised tools. They need accurate, repeatable distances, including at night or in fog, without adding extra complexity in the car.
Starting point
A professional co-driver had a clear idea of the workflow he wanted: GPS-based distances, a reset button on the wheel, and big, instantly readable numbers. He provided the spec and visual direction; my job was to turn that into a reliable iOS app that behaves correctly on the road, not just on a simulator.
Challenge
How do you deliver meter-level GPS distances and instant reset in a moving car?
RallyRec had to feel trustworthy for professional crews. That meant two things: GPS behaviour that holds up over multiple passes on the same stage, and a reset interaction that works every time without distracting the co-driver.
GPS accuracy in practice
Handle GPS noise, tunnels, and varying speeds while still giving distances precise enough to trust in pace notes.
Hands-on-wheel reset
Make the Bluetooth button feel like a natural extension of the car controls, one thumb press, no scrolling, no tapping on glass.
UI for quick glances
Design the app so that a one-second look is enough: big numbers, high contrast, no clutter competing for attention.
Approach
What I did
Focus on one core job
Product scope
Rather than trying to be a general rally toolkit, I kept RallyRec focused on a single thing: distance for reconnaissance. No live timing, no maps, no extra screens, just total and partial distances that stay in sync with the notes.
Result: A simple mental model for pilots and copilots: “this app is for distances, nothing else”.
Tune GPS in the real world
Field testing
I implemented distance tracking with Apple’s location APIs, then spent time driving and testing, including doing loops in my old Toyota Yaris on empty car parks, to validate how distances behaved at different speeds and over repeated runs.
Result: A GPS behaviour tuned on actual asphalt, not just on a simulator or in logs.
Integrate the Bluetooth button
Hardware integration
Using the Flic SDK, I wired the Bluetooth button to the partial reset logic and handled edge cases: reconnection, debounce, ignoring accidental double presses. The goal was to make the button feel like a physical extension of the app, not a fragile add-on.
Result: One reliable interaction: thumb press = new distance segment, every time.
Respect the cockpit reality
Execution
The visual direction came from the co-driver. I translated it into iOS components optimised for quick glances: big numbers, high contrast, minimal text and gestures. I kept interactions as flat as possible so copilots don’t need to think about the app while working.
Result: An interface that behaves like an instrument, not a general-purpose mobile app.
Impact
Integrated into pro workflows
RallyRec is used by rally pilots and copilots during reconnaissance. It became part of their standard toolkit for writing notes and checking distances, alongside more traditional instruments.
Purpose-built for professionals, not a generic consumer app.
Low-maintenance reliability
Beyond the initial build in 2018, the iOS app only needed occasional updates: support for a new Flic button version, and a handful of small user requests. Most of the work was in getting the behaviour right up front.
The app does one job well enough that it mostly gets out of the way.
Hardware + software learning curve
For me, RallyRec was a concrete step beyond “pure software”: shipping something that lives in a car, depends on a physical button, and has to tolerate less-than-perfect conditions.
A different flavour of product constraints than typical apps.
Proof that simple beats clever
The strongest feedback was about simplicity: big numbers, one button, consistent distances. Doing less, but doing it in a way that fits how crews actually work, turned out to be the right trade-off.
No dashboards, no graphs. Just what they need on the road.
What I learned
Building for hardware changes how you test
RallyRec couldn’t be validated from behind a desk. The only way to trust the GPS and button behaviour was to drive, repeat routes, and check distances segment by segment. That feedback loop shaped how I approached edge cases.
Designing for quick glances, not sessions
Most apps assume users will spend time inside them. RallyRec is the opposite: if the crew stares at the screen, something is wrong. Designing for one-second glances forces very hard choices about what’s allowed to stay on screen.
Respecting domain expertise
The value of RallyRec comes from rally expertise, not from clever code alone. My job was to translate a co-driver’s workflow into software faithfully, rather than trying to reinvent how reconnaissance “should” work from the outside.
Simple and robust beats feature-rich
It was tempting to add maps, logs and export features early. Sticking to the core job, accurate distances, one reliable reset, readable UI, is what made the app usable under rally conditions instead of just impressive in a screenshot.