Mid-Level iOS Engineer (Equity) — MustDuo

We believe the gym experience is ready for an upgrade.

The gym hasn't fundamentally changed in decades.

The science has changed. Technology has changed. But the way we experience strength training? Not much.

You still walk into the gym, use disconnected equipment, try to keep track of your own workouts and manually log (only if you remember what you did)

We're changing that by building the next generation of fitness technology to help people train better, understand their performance, and get more out of every workout.

MustDuo is a lifting tracker paired with an iOS app and Naya, your fitness coach and gym buddy (she can't wait to meet you). It tracks reps, movement quality, and progress, giving lifters real data to improve performance and get results.

Learn more:

Our mission: Make the world a healthier, happier, and fitter place.

Where We Are

• Working hardware prototype
• Beta iOS app with active users
• Launched Pre-orders

Our founding team brings hardware, firmware, and software engineering experience from Tesla and Future Fitness.

The Role

Location: LA, or San Francisco Bay Area, New York, or Miami Type: Full-time or part-time

Our Mobile Development Lead has been driving iOS development but is stretched thin as we scale. We're looking for a mid-level iOS engineer to join them and help carry the load - building features and solving problems under their direction, with room to grow into more ownership as you prove yourself. You won't be figuring out architecture alone; you'll have someone to learn from and build alongside.

Our app talks to a custom hardware device in real time over BLE, ingests motion data, and uses on-device/ML-driven models to interpret lifting form, reps, and performance. You'll be working at the intersection of mobile, hardware, and applied ML.

You'll likely be working on things like:

• Building and shipping features alongside our Mobile Lead
• Bluetooth Low Energy (BLE) communication with our custom hardware device
• Helping integrate and iterate on ML models for rep counting, form analysis, and coaching feedback
• New feature development as we grow our user base post-launch (this is a big part of the "why now")
• Bug fixes, polish, and day-to-day app improvements - the unglamorous work that keeps a growing app healthy

What We're Looking For

• Solid Swift/SwiftUI experience - comfortable building features independently once pointed in the right direction
• Some experience with BLE / IoT development, or strong eagerness and ability to pick it up fast (our core product depends on it)
• Interest in or exposure to applying ML/AI in a mobile context (on-device inference, model integration, or similar), full expertise isn't required
• Hardworking, reliable, and self-directed - our lead has limited bandwidth, so you'll need to take initiative rather than wait for detailed instructions
• Comfortable in an early-stage environment: ambiguity, fast iteration, wearing multiple hats
• Genuine interest in health & fitness as well as hardware products is a big plus - you'll ship faster if you actually care about the problem and are using the product

Why Now

We have an MVP, active beta users, and are starting to take pre-orders as we scale up. This is the point where the founding engineer decisions actually compound: the architecture and features you build now become the foundation as we grow. If you want in at the ground floor of a hardware + AI product with a great team behind it, this is that moment.

Compensation

This role is equity-only at this stage (0.5%–3%, standard vesting), full-time or part-time. We're upfront that this means betting on us and in return, you get real ownership, real influence on product and technical direction.