Android/iPhone: The guys behind popular IM client eBuddy have just popped out a sister app that lets you send unlimited real-time SMS messages for "free", and Australia is one of the first countries to receive it.
It's a familiar concept if you've ever used WhatsApp Messenger. eBuddy XMS is a slick-looking SMS replacement service that uses your 3G/Wi-Fi connection to send text messages to your phone contacts and Facebook friends, making it great if you have lots of smartphone data allowance. However, if your carrier only gives you a measly 300MB (which is what I get), it probably makes more sense to use your allocated portion of talk and text for sending SMS messages, while saving your 3G data for actually browsing the web.
Not unusually, its usefulness is limited to those of your contacts who also use eBuddy XMS, which means it'll be a slow start while you wait for your family and friends to jump on board. And it looks like you can't send media — only text-based messages.
eBuddy XMS is exclusive to Australia and the Netherlands (for now), and its available as a free download for Android and iPhone. A Blackberry version is promised soon.