Details are sparse... but reliable sources have indicated that Apple is going to be unveiling a new "communicating device" in the next few weeks... (potentially along side the April 28th announcement)
Reports indicate that the new device will not be a Phone or a PDA. The device will also be able to be connect to PowerBooks, Cinema Displays... though not exclusively -- indicating that it may be used standalone or in conjunction with other Macs.
Apologies for the cryptic information... no other details available.