The entire thing can be built for around ~$35-40.
Here's our parts list: - Raspberry pi 2w for its low power draw, wifi capabilities, decent memory (512mb), and low cost ($15). Also with a arducam - Cheap TTL Aliexpress thermal printer along with sticker thermal paper - Rotary encoder for switching modes, push button for our shutter, and tactile switch for our power switch - I2C OLED display for display our modes and settings - 2 18650 batteries and a 3amp 5v UPS supply, enabling good battery life and regulation. We also add a 1000uF capacity to guard against current spikes from the printer.
We have a longer write up on our devpost: https://devpost.com/software/diffuji?ref_content=user-portfo...
We submitted this for Treehacks 2026, and ended up winning the Most Creative grand prize :)
Alternatively we could use compute from your iPhone, but it adds additional dependencies to external hardware that I don't quite like. We could use a Jetson, but then power draw is quite high. I agree with you that on-device inference is the holy grail, but figuring out the best approach is something we are still trying to figure out.