WhatsApp Messenger, the incredibly popular cross-platform chat, text and email application, is free for download on iPhone for a limited time.

Having been crowned the bestselling app of 2012 by iTunes - and therefore a substantial money-maker for WhatsApp Inc - it comes as a slight surprise to see the software on the App Store for no charge. It has been free on Android for a while, but a yearly fee kicks in after the first 12 months. There is currently no hidden extra cost for iPhone users.

Read: WhatsApp Windows Phone 8 app now available

The news comes after a version of the application finally arrived for Windows Phone 8 users. It too adopts the free for a year, $0.99 per annum thereafter business model. Perhaps that's the plan with the iPhone version eventually too.

Nonetheless, if you want a free way to send SMS-style messages to friends and families, but without the massive battery drain of applications like Skype, WhatsApp Messenger is available for free on iTunes now.