I used a speech recognition system based on Dragon Naturally Speaking to write code by voice. Silvius is an attempt to recreate this system with completely open source software. For more information, see its website: voxhub.io/silvius
The current speech grammar is very basic but usable. For full-time use, one would need to add more commands to the grammar and recalculate the language model. If you are interested in using Silvius, please contact me for details.
I gave a talk at the eleventh HOPE (a hacker conference) about Silvius. The program is here and the recorded video is available here (courtesy of the Internet Society): http://livestream.com/internetsociety3/hopeconf/videos/131671656.
My slides are available here.
A hardware dongle for use with Silvius is under development. Please contact me for details.