Alternate to Google Voice: Line2, Available in App Store

Add a second line to your iPhone with a new telephony app, Line2. The idea behind this app is to have one iPhone and two phone numbers. Line2 and VoIP provider Toktumi, will allow you to have a fully functioning second line, including visual voicemail. Ideal for small business users, and for those of you that really love to talk. It provides a new local number, a ported existing number, or an 800 number.
The app is 99 cents and requires signing up for Toktumi’s “virtual office” phone service at the cost of $14.95 per month with an annual contract, or $19.95 month to month. There is a 30 day trial available.

On incoming calls you see your Toktumi number as the caller ID. When you answer, the automated Toktumi bot tells you who's calling and gives you the option of accepting the call or sending it directly to voice mail, it does require you to activate the iPhone's keypad to make your selection. Outgoing calls are unlimited to the U.S. and Canada and low-cost international calls--all routed over the usual cellular airwaves, not Wi-Fi. Toktumi wants to make it clear that Line2 isn't intended as a "cheap calling solution," but rather an option for business professionals seeking a separate number that integrates with their phone instead of carrying two different devices.

Of course this can be accomplished by using Google Voice, but for that you will need to jailbreak your iPhone/iPodTouch using PwnageTool, Sn0wBreeze, or RedSn0w. To check the status of your device if you are not sure of the model you can use F0recast.

Download Line2 from the AppStore - [Link]