The Apple Watch is one of the best smartwatches on the market, with a whole host of useful features. Wearing a smartwatch can be fun, but building your own watch is more gratifying. The TinyScreen Smartwatch Kit comes with everything you need to build a smartwatch and connect it to your iOS or Android device.
The kit comes with a TinyDuino, TinyShield USB board, a 96×64 color OLED display, Bluetooth, and a 140 mAh battery. The 3D design files for this watch are open source, so you can modify them to build a custom watch case. The complete kit costs under $100 at this time.[where to get it]