I've reworked one of my old shell scripts: the WolframAlpha commandline interface. This client uses the free WolframAlpha API. You can get your own API key at https://developer.wolframalpha.com/portal/apisignup.html (you need it in order to use this script as I'm not giving away my own key). After you've registered your key, put it into script's config section. Here goes a little screenshot to show you the looks of this script interface:
sources are in my Github repo.