Ran across an interesting tip today over at Lifehacker.com, using the Google Voice Activated Search as an instant, speech recognizing calculator and unit converter.
You may or may not be familiar with the fact that you can use the Google search box on a PC to perform math functions or unit conversions. Simply type in something like "four plus four" or 4/2*8 and hit enter. Google will respond back with the answer to your math problem. You can also use it to convert units. For example, you can type 6 liters to cups, and you will get a response saying 6 liters = 25.360517 US cups.
This is a fairly ingenious use of the Google search box, and now, thanks to the voice search feature on your Android phone, you can do the same thing, but using your voice.
For a full write up, and video, check out the lifehacker.com post here.