The kit is a package of electronic parts including a preprogrammed microcontroller chip, and a circuit board. Also included is 2 CR2032 batteries (one spare).
Not from Adafruit Industries: right now we only sell kits.
The majority of the power used comes from lighting up the LEDs that form the numbers. Still, the device should last with 'average use' for a week or longer.
Replacement batteries are easy to get nearly anywhere, and are called CR2032 or BR2032 (20mm x 3.2mm coin cell) and you can replace the battery without losing diggs.
No! The diggs are stored in permanent EEPROM memory: you can replace the battery and retain your precious diggs.
No, the Digg Button kit is a standalone project, it doesn't connect to a computer or the Internet to function (yet!)