10" netbook computer. Something in the same vein as Dell's mini 9 and Asus' Eeepc 1000. 10" LCD, 1.8ghz Atom CPU w/ GMA950 GPU, 1gb RAM (up to 2gb), 8gb SSD with upgrade options for 16gb SSD, 32gb SSD, and 80gb HDD. And OSX, of course.
Also, the trackpad should be a big glass sheet like the new MacBooks, and be removable so you can dock your iPhone/iPod touch in its place to give you mobile data (with iPhone), extra storage space, an LCD touchpad (move various menus to the touchscreen, etc), access to your media files, and whatever else the pairing would allow.
Replace the mini* at a $599 price point, plus upgrade options.
*The mini needs to become a headless iMac. Offer the same specs as the base iMac without the monitor and with a full 5.25" optical drive for around $800-900.