I’ve found a “solution” for the battery problem – USB power pack.
Its output is 5V-1A(Max). It’s mainly for mobile devices but you can also connect to Arduinos, Teensies or Raspberry Pi. The product above is the size of a credit card so quite compact enough to wearable.
Further reading about power supply:
I was doing the “Crystal Ball” tutorial from Arduino Starter Kit. I was tired and I didn’t read the manual thoroughly. When I uploaded the code, the LCD only lit up but nothing happened. I spent 15 min. for figuring out then I realized that potentiometer acts as a contrast controller. Man, how stupid I was….. /@.@\