Mobile comms company Vopium just launched a super-cheap call app for BlackBerrys that routes calls via 3G, Wi-Fi, GSM and GPRS internet networks.
Download the app from the BlackBerry App World and you'll be able to make free VoIP calls (from one phone to another using Wi-Fi) or extremely cheap calls to mobiles and landlines in other countries. Think 2p per minute for both mobiles and landlines to, for example, the US or Hong Kong, and 9p per text.
The app integrates with the address books in your BlackBerry, recognising international numbers and will automatically reroute calls to get the cheapest rate. All new users start with 30 free minutes and 30 free texts.
Vopium recently launched the same app for iPhone, and it's also compatible with Windows Mobile, Symbian and Java platforms.