For nearly 40 years, the Casio F-91W has been a global standard, with its boxy resin case and 7 segment LCD display representing simple reliability. It costs around $20 and tells the time, counts seconds and glows in the dark. But in a world of smartwatches that buzz with notifications and fitness data, the F-91W can feel ancient. Enter the Ollee Watch One, a brilliant hack that replaces the F-91W’s original circuit board with one full of modern features.
Swapping the mainboard sounds scary, but Ollee makes it easy. You unscrew the back of an F-91W, pop out the old board and slide in the new one – no soldering, no electrical engineering degree required. It takes about 6 minutes and the board fits not just the F-91W but also other Casio models like the A158W, F-84W, A159W, A171W and W-59. If you’re not into tinkering Ollee offers pre-upgraded F-91W and A158W models for $99.99 (those are currently sold out) or the DIY kit for $54.99 – a small price to breathe new life into a watch you probably already own.
- 8-Digit Calculator; Constants for addition, subtraction, multiplication and division
- Water Resistant
- 1/100 second stopwatch; Measuring capacity: 23:59'59.99"; Measuring modes: Elapsed time, split time, 1st-2nd place times
What does the new motherboard bring to the table? Bluetooth connectivity, for instance, allows the watch to sync with your phone using free iOS and Android apps. No more fiddling with tiny buttons to reset after changing time zones. An accelerometer tracks your steps and the app allows you to set daily targets, with a loud buzzer alerting you when you hit them. The backlight which was previously a faint green now glows in programmable RGB colours and is a 3 mode flashlight. You also get world time zones, 5 preset timers and alarms that are more advanced than the F-91W’s single loud beep.
The Ollee Watch is open-source so modders can test its limits. Community developers have already created a simple Blackjack game and Ping, a Pong style game where you bounce a pixelated ball across the screen. These won’t replace your phone’s gaming library but are a nice nod to what can be done with a 7 segment display. Custom watch faces and new features are emerging as the community digs deeper into the firmware, making the watch feel like a living project that evolves over time.
Battery life is down from the F-91W’s 7 year run on a single CR2016 coin cell. With the new board and Bluetooth Low Energy and all the extra features you can expect around 10 months or up to 3 years in power save mode. That’s still impressive for a device that can do so much more than just tell time. One quirk: the heart rate feature isn’t what you expect. There is no sensor, instead you manually count 20 heartbeats as the watch times you and it calculates your beats per minute.
Unlike bulkier smartwatches, the Ollee Watch keeps the F-91W’s slim and modest design. The resin casing, water resistant construction and familiar button layout are the same so it still fits under a cuff or with any outfit. This isn’t an Apple Watch competitor, it won’t show your phone’s notifications or run a full app store. The segmented display is limited to text based info and simple images. But that’s the point: it’s a Casio F-91W with just enough smarts to feel modern while staying true to its roots.
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