January 8, 2026
When nerd nostalgia goes off the rails
I hacked Casio F-91W digital watch
Hacker turns $20 Casio into tap-to-pay watch — commenters turn it into chaos
TLDR: A DIY tinkerer hid a contactless payment card inside a classic Casio watch so you can pay by just waving your wrist, but the comments were harsher than any bank security check. Readers argued over the clunky writing, claimed the idea was old, and dragged in the watch’s terrorism lore.
A nostalgic hacker just turned the humble Casio F‑91W — that cheap digital watch everyone’s dad owned — into a tap‑to‑pay gadget, but the real upgrade was the comments section. While the author lovingly explains antennas and payment cards, one reader slammed the writing as “AI vibes” and rage‑quit halfway through, complaining about random bold text like it was an attack on their eyeballs.
Another commenter basically walked in and said, “Old news,” dropping a link to a long‑running DIY watch project, like that friend who responds to your new haircut with “Yeah, I did that in 2016.” Then the internet’s dark sense of humor arrived: someone pointed straight to the Casio F‑91W’s infamous Wikipedia section about its alleged use by terrorists, instantly derailing the vibe from “cute nerd hack” to “oh wow, that escalated quickly.”
Amid the snark, a few practical tinkerers showed up with actual tips, casually suggesting you melt your bank card with acetone to free the chip, as if that’s a normal Tuesday task. Others just wanted nicer backlights in their watches. In classic nerd‑culture fashion, what started as a wholesome story about paying for coffee with your watch turned into a chaotic mix of hardware hacks, security jokes, and “I liked this before it was cool” energy.
Key Points
- •The author modifies a Casio F-91W digital watch to embed a fully functional contactless payment card for making NFC payments via the watch.
- •The project is motivated by frequent travel and the desire to avoid taking out a phone or card, aiming for faster payments at places like public transport and cafés.
- •The article explains that NFC enables contactless data exchange, allowing payment cards to be used without insertion into a PoS or entering a PIN.
- •A contactless payment card contains a secure integrated circuit with CPU, memory, and crypto core, plus an antenna made of materials like copper or aluminum.
- •NFC payment systems typically operate at 13.56 MHz, with some systems using slightly higher frequencies, and contactless cards are passive devices powered by electromagnetic induction.