Touch Mic is an extremely simple app, which turns your iPhone into a microphone.
Connect the speakers to your iPhone's earphone port with compatible adapter, talk into the iPhone and be heard.
Option to either touch screen to mute, or touch screen to talk.
When would you use it? Possible occasions are weddings, KTV, noisy meetings when you need to make an announcement, public speech etc. Or, simply use the standard iPhone earphone to hear what your voice sound like to other people, which is quite different from what you hear yourself.
2G iPhone owners need to use a compatible speakers-only adapter. Do not use speakers/mic adapter because that would disable the built-in microphone.
/* Note */
If you are using the iPhone earphone with built-in mic, only one output channel is active. If you use regular earphones or speakers, both channels are on.