Found an ECHO at my local Office Depot for $12.88. Absolutely neat little credit card sized PDA with Companionlink. Uses stylus and touchpad, a step above the REX.
Synched up with my Goldmine application and brought down my calendar, contact list (which was not easy to do with my Pocket PC).
Came with cradle for serial port and software.
Simple technology, nicely executed, great value (originally sold for $99). The smallest piece of useful technology I've owned.
No hacking opportunity.