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 the company's companion iOS app from the ground up. This is a high-ownership, founding-team role at the intersection of consumer hardware, real-time AI inference, and emotional intelligence. The company is building a first-of-its-kind wearable that reads and interprets a user's emotional state in real time — think a fitness tracker, but for your emotions and cognitive performance. You'll be the primary builder of the consumer-facing mobile experience, translating sophisticated AI model outputs (energy, mood, focus signals derived from audio and biometric data) into intuitive, beautiful interfaces. This role comes with significant equity upside and a clear path to leading mobile engineering as the company scales. The team is distributed, with presence in San Francisco and London . This role is based in London , with flexibility for hybrid or remote working arrangements. What You'll Do Own the companion iOS app end-to-end — architecture, development, deployment, and ongoing iteration. 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 design standards. Integrate backend APIs covering authentication, data sync, and data models. Make autonomous technical decisions as a founding engineer, setting patterns and standards for the mobile codebase. Collaborate across time zones with a small, fast-moving distributed team. What We're Looking For Required: 3+ years of professional iOS development experience with Swift , with a proven track record of shipping production-ready, consumer iOS apps. Demonstrated end-to-end ownership of mobile features — from concept through release and ongoing maintenance. Strong full-stack capabilities including mobile app development and backend API integration. Experience integrating machine learning model outputs or inferences into a mobile app UX. Ability to deliver polished, consumer-grade UI/UX with attention to performance and smoothness. Comfortable working independently and across time zones as part of a remote/hybrid team. Work authorization to be employed in the UK or US — the company does not offer new visa sponsorship (H-1B transfers considered where applicable). Nice to Have: Background in data-driven apps that surface complex model outputs through accessible design. Experience at a consumer hardware, wearable, or health/wellness tech company. Strong CS fundamentals and comfort owning architectural decisions autonomously. Compensation & Benefits Salary: ~$150,000 USD (US) / ~£75,000 GBP (London) depending on location Equity: Meaningful founding-team equity (up to 1–2%) Seed-stage company backed by a top-tier accelerator High-ownership founding role with a clear path to leading the mobile engineering function Location Primary location: London, United Kingdom . The team also has a presence in San Francisco, CA. Hybrid and remote flexibility available for the right candidate. No new visa sponsorship — candidates must have existing UK or US work authorization (H-1B transfers considered).