I have always wanted a pocket-able linux device. I plan to do further iterations but thought it was good to start off with the raspberry pi. I was able to get the thickness down to 2cm including the 3D printed case. To do this, I desoldered the GPIO pins, USB ports, DSI, camera and headphone connectors on the raspberry pi. I also removed the the female header and I2C breakout on the hyperpixel. I took two 20pin lengths of right angled pins and soldered them between the remaining pads of the hyperpixel and the Pi's GPIO. I used a 3000mah lipo for power and Seed Studios lipo rider plus to bump it up to 2amps. I removed the USB port on the lipo rider and trimmed the end of the board to save space. Other than the power switch, there was no other assembly.
It's not particularly usable given the screen size.
W=63cm, L=111cm, H=2cm
Raspberry Pi 4 4GB
Pimoroni Hyperpixel 4.0 Touch
Seed Studio Lipo Rider Plus