We are big fans of NYC's Citi Bike system. However, as engineers and product designers, we can't help ourselves from making it better! For this design hack, we were tipped off by this post on Adafruit's blog, regarding the ability to crack-open Citi Bike's key fob. What if we ported the Citi Bike key's enabling technology (the tiny RFID tag inside) to a new form? Given the general shape requirements for the key fob to work, we wondered: what if you could wear the Citi Bike key as jewelry? To test, we created a necklace prototype to hold the antenna snuggly inside.