IoT Developer for Hardware and App Integration

I'm seeking an experienced IoT developer who can create a hardware device with a digital display. The device should operate offline, providing straight output based on programmed inputs. Key Requirements: - Hardware: - Digital display output - Programmed to do calculation. - App: - Display input data and calculations from the hardware - User-friendly interface Ideal Skills: - Experience in IoT hardware development - Proficiency in app development - Strong programming skills - Ability to create offline operating systems Please provide examples of previous work and a brief outline of your approach.