Per this post in the USA Today, the StartTalking by AdelaVoice app is available the Android Market now or you can download here. According to the presser, the application will allow the sending of text messages with voice even when the screen is dark. Just start talking.
“StartTalking is billed as the world’s first smartphone app that lets motorists keep their eyes glued to the road and hands upon the wheel when composing a text. The company claims that unlike other text messaging apps that require you to peek at or touch the handset at some point, StartTalking is all voice-controlled all the way. There’s no need to open any app or navigate menus. It can even operate when the phone screen is dark or the keypad is locked You simply bark out a pre-assigned name to “wake up” the phone and start StartTalking. Following audio prompts—”Speak to create a text message for Ed or say ‘cancel,'” you can dictate and properly route your message. StartTalking can play back texts too.”