is there such thing as a free software that you download and it make a voice recognition password for you MacBooks or iMacs
There are open source packages for voice recognition. As for whether or not they would be suitable for this purpose, I don't know. Try a Google search.
There are plenty of Voice Recognition Software for Mac
1) MacSpeech Dictate International for Mac
2) TextSpeech Pro Elements for Mac
3) CK's Text-to-Speech to MP3 for Mac
4) MacSpeech Dictate Legal for Mac
more here: http://en.softonic.com/s/voice-recognition-software:mac