Our first plan was a 5 mm card that sticks to the back of your phone. It is the only shape that can pick up the far side of a phone call. It was also most of the cost: a custom thin battery, a dense board and hired design work, about $70,000 of the beta budget on its own.
So we rewrote the plan around a small puck you clip to a collar or hang on a lanyard.
What changed
- An off-the-shelf battery. A 500 mAh pouch cell that anyone can buy, so there is no custom cell to tool or minimum order to meet.
- A day of battery, not a week. A full working day with margin is the target. One open project measured 8 to 11 mA while streaming on the same board, which would give 36 to 40 hours. We have not confirmed that on our own bench yet.
- 512 MB, not 64 GB. At 2026 memory prices, 8 GB of soldered storage alone costs several times what the whole 512 MB part does. 512 MB holds about 43 hours of audio at our planned quality. Storage is now an open decision.
- Phone calls on speakerphone only, for now. The puck hears your side and anything on speakerphone. Calls through earbuds stay out of reach.
Why a puck still records well
Where you wear a recorder matters more than the microphone. On a collar the microphone sits 15 to 20 cm from your mouth, the best spot we found. In a bag or a jeans pocket, fabric and distance ruin the audio whatever the microphone, so we will say plainly that those positions are not supported.
What is next
Measure the battery on our own bench, finish the first printed case, and run a wear-position test that scores transcripts from the collar, a pendant, a shirt pocket and the wrist.
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