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).