Founding Full-Stack iOS Engineer

About the Role A Y Combinator-backed consumer wearable AI startup is hiring a Founding Full-Stack iOS Engineer to own their companion iOS app end-to-end. The company is building a first-of-its-kind wearable device that reads and interprets real-time emotional states, helping users develop emotional intelligence and achieve repeatable peak-performance states. This is a high-ownership founding role — you will define the primary consumer touchpoint for a cutting-edge AI inference platform, bridging complex multi-signal model outputs with intuitive, polished mobile experiences. The team is small (under 10 people), moving fast, and has working prototypes already on users' wrists. The founding team includes ex-Apple hardware product design veterans. The role is based in London (with flexibility for remote) and reports directly to the founding team. Visa sponsorship is not available for new applications; H-1B transfers may be considered where applicable. Candidates must hold existing work authorization in the UK or US. What You'll Do Own the companion iOS app entirely — from architecture and development through deployment, iteration, and long-term maintenance. Surface real-time emotional-state outputs from the company's proprietary AI inference model through clean, intuitive app interfaces. Build and ship a polished, consumer-grade mobile experience that meets high product and performance standards. Make autonomous technical decisions as the founding mobile engineer, setting patterns and standards the team will scale with. Collaborate across time zones with a distributed team spanning London, San Francisco, and beyond. What We're Looking For Required: 3+ years of professional iOS development experience with Swift and a proven track record of shipping production-ready, consumer-facing iOS apps. Demonstrated end-to-end ownership of mobile features — from concept through release and ongoing maintenance. Strong full-stack capabilities including backend API integration (authentication, data sync, data modelling). Experience integrating machine learning model outputs or inference results into a mobile UX. Proficiency delivering polished, consumer-grade UI/UX with attention to performance and smooth user experience. Comfortable working independently across time zones in a remote or hybrid environment. Strong CS fundamentals and the ability to own technical decisions with minimal oversight. Nice to have: Background building data-driven apps that surface complex model or sensor outputs to end users. Experience at a high-calibre consumer tech, fintech, or wearables company. Appetite for a founding-team role at a seed-stage company where your work directly shapes the product and organisation. This role is not suitable for recent or fresh graduates. Compensation & Benefits Base salary: ~$150,000 USD (US) / ~£75,000 GBP (London) Equity: Meaningful founding-team equity package (up to 1–2%) Seed-stage funding from a top-tier accelerator; angel and strategic investor round in progress Location Primary office: London, United Kingdom Flexibility also available for remote work or presence in San Francisco Visa sponsorship: Not available for new applications. H-1B transfers considered where applicable. Candidates must have existing UK or US work authorisation.