Best Microphone for voice recognition project.

This is going to sound really odd.  But I finished a voice recognition program that runs simple computer commands when it hears words I say.  It is implemented in a small room in my office.  I don't want to wear a mic or carry a mic around to control the program (plus I want to impress the boss).  Is there a microphone that is powerful enough to hear what I say no matter where I am in the room?  I am guessing it would have to be something with a preamp etc.  I just want to be able to give a command (I know I will have to talk loud, but i don't want the scream) and the mic relay the sound to my computer.  I have tried normal mics and they don't even pick up if i am yelling. I don't want to spend more than $50.  My program doesn't make any mistakes, so don't worry about background noise, it can sift through it. Thanks.