Onnit Studio · iOS, Android & web apps
I design, build and launch iOS, Android and web apps for founders, small businesses and teams that need an extra developer. You work with me directly, start to finish.
Receipt-scanning rewards app. I joined the team to build out the app side, worked to implement a new design, audited the codebase, fixed what needed fixing, redesigned the onboarding and ran ASO across six regions.
Result#1 for “cashback card” in several countries.
Took over an app a previous team had left broken and slow. Went through every problem with the lead developer, fixed them and shipped it.
ResultRunning smoothly in production.
Client app · 2024
Brand, design, build, ASO
Catalogue and collection tracker for 84,000+ football shirts.
ResultAt or near #1 for football shirt searches on both stores.
Client app · 2025
Design, build, launch
Portfolio tracker for whisky collectors, with live prices pulled from retailers and a price history for every bottle.
ResultLive on iOS and Android.
Client app · 2025
Brand, design, build, launch
Meet people nearby who share a hobby and are free at the same time.
ResultLive on the App Store.
Platform for martial-arts promoters to find fighters and fill fight cards.
ResultLaunching soon.
Got an app in mind?
iOS, Android or web. I design it in Figma, build it, and get it live. We agree the price before I start, so there are no surprises later.
Slow, buggy or stuck? I go through the code, tell you straight what's wrong, and fix it.
Need another React Native developer on the team? I work remotely and I'm flexible on how long for.
A 30-minute chat about your idea. You leave with a plan and a fixed quote, whether we end up working together or not.
You see the designs before anything gets built. Then a few rounds of building and feedback until it feels right.
I handle the App Store and Google Play submissions, or put your web app live.
Launch is the start. If you want, I stay on to keep the app healthy and help people find it.
Plans start from around £65 a month and cover:
It's SEO for the app stores. The keywords, description, icon and screenshots decide whether your app shows up in search, and whether people tap install when it does.
It works. Shirt Squad sits at or near #1 for football shirt searches, with around 130k Google Play impressions a month. GreenCart is #1 for “cashback card” in several countries, at around 34k a month.
Sebastian was responsive, solutions-focused, and genuinely invested in getting the details right. He helped turn a complex idea into a clean, functional app without unnecessary complexity.
Communication is on point and exceeds my expectations with every new feature or update. I couldn’t be happier.
Did more than make my idea come to life, it improved it by injecting genius ways.
It depends on what the app needs to do. After a short call I give you a fixed price before any work starts. If the budget is tight, a no-code or low-code build can bring the cost down, and I'll tell you if that's the better route.
Most apps take 4 to 8 weeks from kickoff to launch. You get a timeline on the first call.
React Native for iOS and Android, Next.js for the web, and Supabase, Firebase or Node on the backend. You own all the code. For tighter budgets I also build with no-code and low-code tools.
Yes, that's a good chunk of what I do. I start with an audit so you know exactly what's wrong and what it will take to fix, before I change anything.
Yes. Remote, and I'm flexible on how long for. Recent contracts were with VeChain and Linfa.
Bug fixes right after launch are included. After that there are optional monthly plans for updates and App Store Optimisation.
I read every message myself and reply within a day.