For a while we worked on this project in parallel with uECG - but more than a year ago shifted our focus and made very little progress since then.
Yet people asked about EMG and we decided to make at least something by using uECG as a sensor, by adding more processing - both on the device and on the PC. But also it became clear that we need a specialized device: wearing many different units wasn't convenient and data stream wasn't synced well enough.
Even though we had a (mostly) working PCB which produced good enough signal, it still was extremely inconvenient to wear - in a way, even worse than 4 separate uECGs - so it didn't really solve our problem, it only was a rough first prototype.
We started with a PCB design, considering various shapes - among our options there were ovoid, triangle, rhombus, trapezium, plus-sized oximeter, and some unspeakable curves of all kinds. Discussion took unreasonably long time and at some point Olha just created "bullet" variant that took into account all weak points of other designs, and here we are.
We introduced some changes into schematics as well, and took a new approach to PCB design - after (finally) learning about behavior of EMF propagating between traces and ground plane we minimized length of gaps there (by creating more, but shorter, gaps) - thus reducing inducted noises (hopefully).
The PCB is going to production next week, so there will be more updates relatively soon!