MustDuo is a smart hardware tracker and AI coach for serious lifters. It attaches to gym equipment or clothing, automatically counts reps, plans your workout, and gives real-time coaching — no manual logging, no guesswork. We're a small team of ex-Tesla engineers building hardware and software from the ground up, and we're now taking pre-orders and scaling toward launch.
We're not pitching an idea - we have a working MVP, real beta users training with it today, and pre-orders coming in.
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.
This isn't a typical CRUD-app iOS role. 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.
• 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
• 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
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.
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.
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