BlackBerry Messenger is one of the biggest advantages to BlackBerry smartphone ownership, and one which makes other phone users a little jealous.  Although we’ve heard in the past RIM may bring a BBM app to the iPhone App Store, nothing has appeared so far.  There are however, several cross-platform messenger applications available, all of differing quality and ability.

Whatsapp is up there with the very best you can get, and up until today it has been reasonably priced at $0.99/£0.59; however it has just been reduced in price to absolutely nothing!

Interestingly, the app has been free on most other platforms for ages – BlackBerry and Android for example – so this could be a permanent move for the iPhone version too.  If you’re interested though, don’t wait around just in case it goes back up again tomorrow!

It’s a breeze to setup and use, as all you need to do is enter your phone number and a PIN sent from Whatsapp by SMS, and that’s it.  The app then scans your contacts to see who else uses the service, and places them in a favorites file.  Conversations take the form of threaded exchanges, just like the iPhone’s own SMS app, and you’re alerted by Push notification of new messages.  You can even chat in groups and send media files too.

Using Whatsapp is free over Wi-Fi, but does use data over your cellular connection, and doesn’t have any hidden charges for international messages, extra features or anything else.

Many of you will have already given Whatsapp a try, but for those who’ve been put off by paying for the app, now’s the time to download it and encourage your friends to do the same!