Skype for iPhone is an app that lets you use the Skype service to send instant messages and make voice calls for free to other Skype users, and to make low-price voice calls to cell phones and landlines around the world. You have to use Wi-Fi to make voice calls--the voice service won't work over 3G mobile networks--but that effectively means free iPhone-to-iPhone calls (using Skype and Wi-Fi), low-cost international calls from and to anywhere in the world (again, with Wi-Fi), and voice calls for iPod Touch users even (with an additional microphone, and while connected to Wi-Fi). Call quality depends on your bandwidth and Wi-Fi connection, but the audio is often even clearer than with conventional calls, especially internationally.
The app's interface is slick and intuitive--arguably more so than the Mac and PC Skype clients--and you can quickly see the status of your contacts, start IM conversations (over Wi-Fi or 3G), add pictures from your phone to contacts (which almost instantly syncs to your computer client, as well), and access your profile and voice mail. At this time, iPhone does not support push notifications, which makes it impossible for Skype calls to get through without the app already running. Still, anyone who would like to cut down on their minutes can have their friends download Skype and talk as long as they want over Wi-Fi. When the iPhone 3.0 update comes out, this app will likely receive a more favorable review.