With Apple's release of SIRI, there has been a tremendous increase in demand for a similar Android application. In response, a number of developers have begun trying to cash in on this latest trend. What most users seeking these apps fail to realize, is that android has a great many of these features built right in.
Android's voice dialer has the ability to open any app simply by saying open "application". There are limitations to this feature, and the phone will not yet speak back to you. It will always followup with a prompt asking you to confirm the specified action, which leaves us lacking true "hands free" operation.
Voice Search by Google
Believe it or not, this feature can be used to send text messages, although it still requires a bit of on screen interaction to get it right.
You can activate the Voice Search and say send text "whatever message you want here" and it will open a slightly different messaging window with the text already entered. You still have to also either click on the proper field, or manually select a contact, but this is a start.