Once the BT Fon app has been downloaded to a handset, users simply enter their BT username and password, and from then on they will automatically connect via Wi-Fi when within range of a BT hotspot. All BT Total Broadband customers get free unlimited access via BT Wi-Fi hotspots.
"Millions of BT Total Broadband customers already get free access to the UK's biggest Wi-Fi network. This free app makes accessing Wi-Fi so simple you don't even have to think about it," said John Petter, managing director, for BT Retail Consumer.
"This represents real value to our customers at a time when more and more people are using their mobile phone to access the internet."
BT has also revealed that it will donate 50p to Children in Need for every BT FON app downloaded, up to a limit of £10,000.
For more information visit BT's dedicated webpage.