Most iPhone users can take advantage of tariffs that include a certain number of free call minutes each month, but after this allowance has been used up, it is a matter of paying by the minute to speak to your contacts. iCall Free VoIP, as the name would suggest, enables you to make even more free calls - even from an iPod or iPad.
The app can be used over a 3G or wifi connection and includes free ad-supported calls to the US and Canada from within these countries - hopeful would-be-users in other countries will have to wait for better international support.
With the likes of Skype and Google Voice offering VoIP calls , apps such as iCall have to offer something interesting in order to stand out from the crowd. US phone users can use the app to make free phone calls to any phone number - not just internet numbers or email addresses.
There are also a number of paid for bundles available which can be used to make low cost international phone calls and avoid roaming charges. This is not a perfect app, nor a complete phone replacement, but it is worth having installed for a backup.