Well let's separate both microphone signal amplification and output amplification. I think the former one is the one we should focus on.

@TiagoTiago: The guitar doesn't need power. What happens is that the guitar's pickups carry the signal to the wire coming out of it, similar to a microphone that singers use. So the basic concept is amplifying the guitar signal (like you would a normal voice through the mic), and then apply some audio processing on it.

I use GuitarRig [URL]http://www.native-instruments.com/[/URI] for that. And what i do is, I plug the end of my guitar to the mic input of my pc, then start up guitarrig which does what i stated above. If i want to amplify the output i simply plug my pc to a speaker box, otherwise headphones would do.

I think the first step to solve this microphone amp business is to connect the guitar input to the microphone section of the 3.5 inch jack. And see if the microphone catches some guitar tones (using recoreder app for example) Won't have time to do this anytime soon due to work, uni, and some traveling but if someone wants to chip in on this it would be awsome