Voice recognition APIs, will Google Voice do this?

Question

I've got an idea for an android app, I want to be able to say commands and have the application listen out for these and perform some action.

For example, I want my app to sit idle and listen for my voice, when it hears me say "start", the app will start doing something until I say "stop".

The idea is to lay the phone down and not have to physically touch it in order to control my app.

Would this be possible with any current APIs? If so which ones should I look into?