First app, DTMF Dialer allows you to dial phone number without physically dialing them on the phone you are dialing from. This might seem a little weird, but it can be classified more as a party trick than a really useful application. When your phone makes tones when you press buttons, this application will emulate the dialing sounds. The "phreakers" would do back in the day to pay phones when these people wanted to make free phone calls. This method was fixed, and nowadays, modern phones don't support DTMF tones no more.
Using DMTF Dialer,you just have to put the iPhone's speaker to the mouth piece of a normal phone and choose the number for dialing from your contact list. DMTF Dialer will play those tones, the sounds that the phone picks up and calls.
The newer version, 1.2. brings new features like prefixes. Sometimes you will want to use this application when you are at office, and you have to dial 9 to get a dial tone, and this application supports setting up three custom prefixes, and you can also set one to be the default for your calls. In order for DTMF player to work properly, you should set up the iPhone's speakers volume to 75%.
Another application you can use for DMTF tone dialing on your iPhone is DTMF Pad, which has a very simple functioning sequence. You should put the speakers of the iPhone close to the mouthpiece of the phone, and the DMTF-tone sound will dial. This works on iPods too, and iPod users might find it useful too. This application can also be used for testing another application "Flick'n'call". You can check the DMTF function for working with your environment and then you can purchase "Flick'n'call". When you use this application with iPhone, pay attention to the volume. Too small or too loud might not work, but you can set a smaller volume, and then gradually increase it to the perfect level. On iPods, the Speaker of the iPod is required for a proper functioning of this application.