UK fixed-line giant BT is the latest firm to offer a VoIP app for smartphones, announcing the launch of BT SmartTalk as a free app for iOS and Android devices.

The big selling point is the ability to link the app with a BT fixed-line calling plan, enabling users to effectively use their fixed-line minutes and deals via smartphones.

The app “works best” over Wi-Fi, but will also work over any mobile data connection, the telco said. Subscribers to BT’s broadband service will also be able to use the app at BT’s 7.5 million hotspots worldwide.

BT claims SmartTalk is the “the first app launched in the UK to link an iPhone with a customer’s home phone calling plan”.

By billing users as if they were calling from their BT landline, the operator claims that the app will enable users to make savings compared to standard mobile calling rates in several ways.

It provides an example: “Customers on BT’s Unlimited Anytime Plus Plan will be able to make 24/7 calls to any UK landline number or 0845 number at no extra cost, whilst enjoying calls to mobiles from as little as 2.65 pence per minute – a fraction of the standard rates typically charged by mobile pay as you go tariffs.”

When travelling abroad, BT customers can also use SmartTalk to phone back home at the same rate as they would if using a landline, the firm says.