We will never pay for a text message again, no matter where we are in the world. Instead, while traveling, we use this money-saving app to send unlimited free texts. All you need is a Wi-Fi or 3G connection to send texts and group messages, and share photos, videos, and audio clips. You — and your contacts — must have the app (similar to using Skype), but texts can be sent between any kind of smartphone.
$.99 for iPhone; free for the first year (then $.99 a year) for Android, BlackBerry, Nokia S40, Nokia Symbian, Window Phone; www.whatsapp.com.