Seems I was right.
Something as common as a mouse / joystick is always standardized, and there's really no reason why the Pandora wouldn't support the HID standard for BT. I mean, it's a standard.
My wife has an Asus EEE running Linux (Ubuntu Jaunty Netbook Remix) and a Microsoft Bluetooth Mouse. It takes a little while to figure out how to set up, but once it's working it's pretty rock solid.
I'm sure someone will be able to document the process and give help when needed.