Building with AI
A small collection of the products I had wanted for years, and could finally build once the cost of starting fell.
Derek Fidler20268 min
For most of my career, an idea had to clear a high bar before I could act on it. It needed to be important enough to justify a team, a roadmap and months of engineering time. That left a long list of small, useful products in my head: things I would use every day, but could never quite justify building.
AI changed the maths. I can now make a real version quickly enough to find out whether an annoyance is actually worth solving. These apps are not concept work. Each one has forced me to learn the parts of product development that used to sit just beyond my reach: authentication, bank connections, health data, OAuth, native platforms, distribution and the unglamorous work of earning trust.
The collection now ranges from personal finance and cooking to language learning, local discovery and a personal assistant. Each product has its own home on the web, where the idea can be understood and the working product can be opened directly.
Practising judgement
I am not building for the sake of building. The point of the exercise is to practise judgement. When making becomes cheap, it exposes the part that was always difficult: deciding what deserves to exist, what should be left out, and what needs to be true before a product is genuinely useful.
Each app gives me another set of reps across hundreds of small decisions—where to begin, what to simplify, which edge cases matter, how the interface should explain itself, and when the value is real enough to stop. Once I reach that point, I move to the next problem. The apps are the output; the compounding skill is judgement.

Personal finance · Web & iOS
Piggy
A personal finance system that combines envelope budgeting, bank sync, and long-range planning. Piggy connects what is safe to spend today with where mortgages, investments, and retirement choices are taking you.
Open Piggy
Recipes · iPhone, iPad & Mac
Dinnr
A recipe book for everywhere you cook. Dinnr turns links, videos, screenshots, and cookbook photographs into clean recipes you can save, plan, and follow without distraction.
Visit Dinnr
Fitness · iPhone
Fit Habit
A quiet workout tracker built around consistency rather than streaks. Fit Habit logs sessions on a calendar, detects personal bests, imports Apple Health activity, and makes body-composition trends easier to read.
Visit Fit Habit
Tasks · iPhone & Apple Watch
Do It
A priority-first task manager for iPhone and Apple Watch. Natural-language capture and four simple priorities keep the day ordered without forcing people to maintain elaborate lists.
Visit Do It
Local history · Web
Amsterdam on Foot
A location-aware walking guide to 23 places that explain how Amsterdam became Amsterdam—from medieval pilgrimage and republican government to trade, finance, and empire.
Start the tour
Local discovery · Web
Lekker Plekken
A personal map of Amsterdam restaurants, cafés, and bars. It ranks more than 900 saved places using distance, opening hours, weather, and whether a place is actually worth trying next.
Find a place
Language learning · iPhone
Dutch Primer
An audio-first Dutch learning app built around native voices, focused listening, and spoken answers. It minimizes screen time and gives pronunciation feedback without retaining recordings.
Visit Dutch Primer
Personal assistant · Web
HeyHey
A personal assistant that connects the tools already in your life—calendar, inbox, tasks, home, notes, and weather—while keeping data access deliberately narrow and the controls yours.
Open HeyHey