VoiceActivator adds full-system voice control to the iPhone
VoiceActivator will allow you to retain the original function of Voice Control, but also create customized system actions, like opening particular webpages, apps, etc. The only caveat is that VoiceActivator will only work on jailbroken devices, including the iPhone 4, iPhone 3GS, iPod Touch 4G, and iPod Touch 3G.
The app is available now from Cydia under the BigBoss repository for US$4.99. But we have to ask, shouldn't the iPhone already do this?
source: Redmond Pie