Updating contact pictures on android
If you are using different one, you may need to use different graphic libraries and modify arduino source code. The most ideal battery depends on what size of watch you want to make.
It would be helpful for you to prepare the assembly manual.Preparing for Android Android v.4.3 supports the service that is used to get notification information from an app.So Retro Watch app is based on Android v.4.3 to enable notification service.Korean user Wonho made this based on Adafruit_SSD1306 driver.
https://github.com/wonho-maker/Adafruit_SH1106In this case you must modify codes like below. If you wish to use various display, use u8glib instead.
In order to use it, you must install Adafruit_SSD1306, Adafruit-GFX-Library.(According to your development environment, Adafruit library conflicts with Robot_xxx library.