New improved Line2 app has added unlimited text messages at a lower price.

Line 2, an iPhone app that allows you to make phone calls with your iPhone using a Wi-Fi hot spot wherever there is a weak cellphone signal and to turn an iPod Touch or iPad into a full blown cellphone for as little as $15 a month, has gone through some enhancements and is now better than before.
At a cost of $10 a month, Line 2 gives you a second phone number for a second phone line complete with its own contact list, voicemail while turning the iPhone into a dual-mode phone which means it can make and receive unlimited calls for free Wi-Fi connection.
The new and enhanced Line 2 have features like the possibility to delete recent calls entries, transfer incoming calls to your Line 2 number to your iPhone's when Line 2 is not running. The new Line 2 app will also you to send and receive unlimited text messages when in a Wi-Fi hot spot even without an AT&T text plan according to the New York Times.

For more, see NewYorkTimes.com