Vonage has released a new iPhone app that enables you to call any of your Facebook friends for free.

VoIP apps from the likes of Skype are already well established in the iPhone ecosystem, but this latest application from Vonage takes it one step further.

The only potential problem being – do you really want any of your 'friends' on Facebook to be able to contact you at any point on your mobile phone?

iPhone and Android

You can see a video demo of Vonage's new app over on the company's website, available right now for the Apple iPhone, iPod Touch, and iPad and Google Android devices.

The Vonage app integrates seamlessly with your Facebook network, populating your contacts list with your Facebook friends, so you can call them (if they have the app on their device) or IM them at any time.

You can grab the Vonage app from the Apple App Store and the Android Market right now to test it out for yourself.