AVR-Chat

Here is my proposed device. This is an art project. 
Device is portable and battery powered. 
It has a LCD display. 
It stores digital "messages" in memory. Messages may be text or image. These
messages are displayed on the LCD.
The contents of the message memory needs to be edited on a PC and
uploaded/downloaded via bluetooth.
In addition, anytime the device comes in bluetooth range of another instance
of the same device, it will send a message of up to 64kBytes and possibly
receive a message the other device is trying to send.

What dev tools/kits do you recommend?