Keeper

Inspiration from the suffering

Like most students in South Korea, I spent my teenage years sitting for long hours in classrooms and study halls. Combined with too little movement, it led to scoliosis, which I still feel today. At Korea University’s Ergonomics Design Lab, I started asking a different question: could we improve posture without asking people to move more? That led me to the one object everyone sits on all day. I stopped seeing the cushion as part of the chair and started seeing it as a product of its own.

Shaping an ergonomic foam

Good posture is a habit, and habits are hard to build. I wanted Keeper to give gentle, real-time feedback through sensors. But no amount of smart technology could make up for an uncomfortable cushion, so I started with the foam. I analyzed dozens of existing cushions for density, elasticity and contour, and designed a four-layer structure that supports alignment while still feeling comfortable.

Integrating IoT intelligence

Next, I put sensors into the cushion. We embedded 32 force-sensitive resistor (FSR) sensors that detect 11 sitting postures, from leaning forward or back to crossing your legs. Early prototypes ran on Arduino boards. For mass production, I brought in hardware partners to design a custom PCB shaped to the cushion, with a Bluetooth module and MCU for stable, low-latency data to the app.

Designing the companion app

My first version of the app was built to be engaging: animated real-time posture feedback and detailed charts. It was a hit at exhibitions and demos. But once crowdfunding backers started using it every day, the constant alerts became a distraction. So I redesigned the app around one idea: stay in the background. The app now handles calibration, posture tracking and simple daily summaries, and the cushion itself does the nudging with a gentle vibration.

Calibrating with real-world data

After launch, we collected posture data from over 200 users and found a problem: the measured posture often didn’t match how users felt. Readings varied with age, body shape, clothing and sitting habits. So I moved from absolute readings to personal calibration. When pairing the cushion, users sit in their correct posture for five seconds to set a baseline, then mimic their usual bad postures to define their own ranges. The cushion vibrates only when someone stays out of their range for too long. After the change, 93% of users said Keeper measured their posture reliably.

Reflection

I left the lab to work on Keeper full-time in early 2020, just as COVID-19 hit. Factories shut down, production slipped and money was tight. With help from mentors, my team and early backers, we secured government grants and private investment, finished the product that year and launched in 2021.

Keeper taught me that hardware is as much about people and persistence as technology. It also taught me the cost of over-engineering: my first app tried to do too much, and users told me so. Keeper didn’t become a commercial success, and I wound it down. But the team and I joined Charco Neurotech to keep building health products, this time for people with Parkinson’s.