The Pebble is an all-in-one Arduino-compatible Development Board, designed to be a very versatile experimenters and learning board! It can even go wireless for all kinds of other gadget applications.
Including a 20 x 4 character backlit LCD, rotary dial and separate RGB LED, you can get feedback from your programs and applications right on the Pebble.
Temperature and light sensors are included, it connects straight to USB for power and programming, and includes a battery operation power supply to run from 2 AA cells or similar.
As a wireless sensor node, you can plug an XBee wireless module in and make your Pebble a remote wireless gadget!
If you'd like a touchscreen input for an LCD or controller, the Pebble also has a touch screen input connector that is compatible with the touchscreen overlay used in the popular Nintendo DS. These touchscreens are available separately from many sources.
Lastly the Pebble includes standard Arduino footprint headers, on-board USB programming and communications, and two open-collector outputs for driving connected lamps, LEDs, relays and other stuff.
Note that because the Pebble has so many features included directly on the board, the shield header sockets are mostly reserved for onboard functions and the headers are provided to allow connection to the on-board hardware signals. The Pebble is not generally compatible with most shields due to the pins being used by the on-board hardware, though there are some I/O pins like the 4 touch screen pins which can be used as general analog in or digital I/O pins if a touch screen isn't being used.