Standalone Handheld Device Creation

I’m developing a dedicated handheld that will operate offline. No Wi-Fi, Bluetooth, cellular, or any other radio is required, so the entire design has to function in isolation. Because of that restriction I’m open to whichever operating system keeps the footprint light and the boot time quick, whether that’s a stripped-down Android build with networking stacks removed or a fully custom OS. but more likely just on/off. then a button to run. Your task is to take the idea from concept to a working prototype. I’ll need the electronic design (schematic, PCB layout, and component selection), a daylight-readable display, a rechargeable battery able to power at least eight hours of continuous use.. Low power consumption, immediate on/off and rock-solid stability. Deliverables • Complete bill of materials and Gerber files ready for fabrication • Firmware / OS image with reproducible build instructions • 3D-printable enclosure files • Step-by-step flashing and assembly guide • One post-delivery revision round based on test feedback Acceptance criteria: an assembled prototype that powers on, launches the demo app in under five seconds, and runs for eight hours on a single charge, all with radios fully disabled. If you’ve previously built low-power products—please share examples. I’m excited to see how you’d bring this offline handheld to life.