This Wireless Numeric Keypad with Track Ball is a fairly stylish add-on for your netbook. Works over 2.4GHz RF, needs a pair of AAA batteries and has a bunch of the usual shortcut keys you find on most keyboards including media playback, volume, mute etc. Works with Windows only, XP and later. US$36.90
2.4GHz Wireless RF Numeric Keypad With Tracking Ball has 19 keys and 17 hotkeys to provide a comprehensive keyboard for the users on the go! It is small, slim and portable that is suitable for travellers.