When the iPhone was launched, one of the major gripes about it was that it didn't have a voice dialing function. It didn't matter if you had a Bluetooth headset that could handle it or you just wanted to press the button on your iPhone headphones, Steve had decided to leave that feature out. The SpeechCloud Voice Dialer app has proven that it's worth it to wait for Apple to enable this feature or perhaps just wait until the apps can stay open in the background.
The SpeechCloud Voice Dialer app requires you to open the application, hold a button, say ?Call? plus the name of the contact you want to call, then let go. Regardless of whether it can actually understand you or not, the app takes a good 30 seconds before it even lets you know the results of its search. If your lucky enough for it to actually find the contact you're looking for, it then brings you to another screen with that individuals name and phone number for you to press and begin the call.
It is currently not possible to do voice dialing any other way than by opening this application directly. To go from sleep mode to actually making the call using this method would require more time and patience then simply finding the contact in your phone book. The limitations of this application don't come solely from the iPhone itself, as it does force you to then select the phone number that you want to dial before it will actually call.
The idea for a voice dial app is something that will need to be improved upon. Unfortunately, it doesn't look like there will be anything great coming out that can properly offer this functionality from a third party. This app is something that should not be on your iPhone.