A small team of engineers from Stanford and New Mexico State University released a free app which makes typing Braille easy on tablet computers.

The app registers the location of all the fingers when the user simply places all the fingers on the screen before typing. Lifting the hands off the screen and placing them back recalibrate the keys.
The app does few other tricks like easy undo by simply twisting one of the fingers on the screen, launching Google with a keystroke and a simulated voice reads out the results of searchers. The app can support many of those including different languages and scientific and mathematical formats since there are a variety of Braille standards and alphabets.
Source-Medindia