Give Your Casio F-91W a Brain Transplant with the Owatch

Do you ever find smartwatches to be too smart? With a display barely larger than a postage stamp, does it really make sense to read emails, browse social media, or navigate other complex apps on your wrist? Including all of this functionality bulks up the size of the device, and the powerful hardware required for these features drains the battery in no time. Remember when a tiny coin cell battery kept your watch ticking for years on end?

Cam Shand wants to give us another option — something in between a modern smartwatch and a classic digital sports watch of decades past. He has designed what he calls the Ollee Watch (Owatch) module. This module fits perfectly inside the case of a Casio F-91W wristwatch, replacing the original hardware to give it modern (but not too modern) capabilities.

The new board features a dual-core CPU, pairing a Cortex-M4 processor with a low-power M0+ core. This combination allows the device to handle tasks like simple games and data processing while still maintaining excellent energy efficiency.

The upgraded watch includes an onboard accelerometer for step tracking and gesture controls, as well as a temperature sensor capable of logging environmental data throughout the day. Bluetooth Low Energy connectivity enables syncing with a smartphone for time updates, settings, and firmware improvements — without requiring cloud accounts or other online services.

The hardware upgrades extend to the user experience as well. A customizable RGB backlight replaces the original dim green glow, while a louder piezo buzzer enables more distinctive alarms. An optional NFC tag can be installed behind the display, allowing users to trigger smartphone actions with a simple tap.

Installation is designed to be easy for hobbyists, taking around 10 to 15 minutes. The process involves opening the watch, transferring battery terminals, and inserting the new module into the existing housing. Beyond that, users can further personalize their device with 3D-printed cases, tinted display films, or alternative straps.

Functionality goes well beyond basic timekeeping. The Owatch includes fitness tracking modes, interval timers, sunrise and sunset data, and even retro-style games like Blackjack and Pong-inspired “Ping.” Yet, perhaps its best feature is battery life: up to 10 months with regular use, or as long as three years in power-saving mode.

The Owatch is selling as a kit for $54.99, or you can purchase a complete watch for $99.99.