The Executive Desk Companion, made by Franklin, is a combination speller, thesaurus, calculator, and clock. It's navigated via three buttons on the front or by tapping the screen's display with a stylus. If you're waiting for me to say that doing this is going to get you someplace that the PDA you navigate the same way can't, don't hold your breath.
The speller has over 100,000 words, and the thesaurus incorporates 500,000 synonyms. If you are waiting for me to mention ...