This Line2 app was just approved after a 3 month delay, partially caused by the Google Voice shenanigans Apple pulled back in July when they pulled out all the Google Voice apps from the App Store. This is really similar.
Toktumi works similarly to Google Voice, letting you use one virtual number to forward to your real numbers. It doesn't support SMS, and it costs $15, but it supports business features like phone trees and other filtering options. The Line2 app is by Sean Kovacs, the guy who made "GV Mobile", the Google Voice app we still use on our iPhones now.
It's strange that there's a double standard for these apps in the app store when they're so similar, but it could be the missing SMS functionality that makes Toktumi more appetizing for Apple/AT&T when compared to Google Voice. [Tech Crunch]