Heat Stress Wearable Prototype

I’m building a compact, wrist-style wearable that keeps workers safe by tracking three key indicators in real time—skin temperature, heart-rate and sweat level—and then quietly buzzing whenever heat stress crosses a preset threshold.

The core requirements are straightforward:
• Continuous measurement of temperature, PPG-based heart rate and a sweat (GSR) reading, with optional fall detection already sketched into the concept.
• On-board processing that fuses those signals into a simple heat-stress score.
• Instant vibration alert (no audio or visual cues) when the score is high, plus an LED or BLE packet confirming the event.

I will need schematic and PCB layout, firmware that handles sensor polling, data fusion and the vibration trigger, and a fully assembled proof-of-concept I can field-test for at least an eight-hour shift on a single charge. If you already have experience with low-power MCUs, BLE modules, PPG and GSR sensors, that’s perfect—I’d like to iterate quickly and validate accuracy against a reference thermometer/heart-rate strap.

Deliverables
1. Complete hardware design files (schematic, Gerbers, BOM)
2. Well-commented firmware source, ready for OTA updates
3. Tested prototype with short demonstration video showing a triggered vibration alert

Acceptance criteria
• Temperature, heart rate and sweat readings update ≥1 Hz
• Vibration alert fires within two seconds once the heat-stress threshold is exceeded during test conditions
• Device operates eight hours on a single charge with Bluetooth advertising enabled

If you can meet those checkpoints, let’s talk timelines and component choices so we can move straight to board spin #1.