I don't know about speakers (i'm sure you can..) but it does work pretty nicely as a tablet (that runs Mathematica!)
If you type "raspberri pi tablet" into a search engine you'll find Michael Castor's tablet:
http://www.mkcastor.com/2014/01/02/pipad-build/
I tried making my own, but made the cool, yet shortsighted decision to make it out of granite so it would be a "stone tablet". Granite tiles are cheap, but the tools you need to cut them are not. Plus it ends up being really heavy... I plan to remake the case one of these days out of something lighter.
I wrote up how I did it, and there are some tips in there that you may find helpful (like figuring out an on-screen keyboard).
Here's the link:
http://meanderinglaser.weebly.com/raspb ... he-pi.html
http://meanderinglaser.weebly.com/-tablet-build.html