Droid (and Android OS) has voice to text built in.
Using Handcent (and probably the built in sms program, I haven't used it), I can easily respond to an SMS by tapping on the microphone icon, instead of in the text box, and a window appears, asking me to speak clearly.
I then simply speak, and what I said is entered into the text box. Hit send and your response is sent.
Google search allows you to say something, and have it entered into a search box and launch your browser to show related results.
Say "Navigate to Bob Smith", or "Navigate to Best Buy", and the Droid launches Navigator, and either starts giving you directions to Bob's house, or displays several Best Buy stores near you. Tap on the one you want to go to, and again, Navigator launches and begins giving you verbal turn by turn directions to that Best Buy!
There's also a translator program (free), say something in english, it'll translate it into Spanish and speak it out loud (or german, italian, french)...
Not sure if this is what you had in mind.