Line2 may be the first to break the trend. Via the app, users can use their iPhones to make phone calls, send text messages, create multi-caller video conferences. Users can either port an existing phone number in or create a dedicated one.
Sounds expensive, but it actually isn't too bad. The basic Line 2 service runs for $10 a month or $100 a year, while the more involved Line2 professional plan, which includes contact management and a "virtual receptionist" runs for $150 a year.