BT has launched a mobile voice-and-email service - that uses WiFi where possible to reduce cellular voice and data bills.

"This service uses WiFi to give users free VOIP calls, whether they subscribe to BT Openzone or not," said BT spokesman Les King. It includes an HTC S620 Windows Mobile PDA/phone, the "BlackBerry-killer" HTC launched last October, with a VOIP (voice over IP) installed by BT.

BT's Office Anywhere is up against push email services from T-Mobile, Orange, Vodafone, including one based on the Palm Treo. The difference is that BT has wrapped it up in a package aimed at small-to-medium businesses, with up to 200 users. Also, as BT does not run its own mobile network, it won't be pushing users towards high mobile voice and data charges.

"We aim to give customers the best connection - as fast and as cheap as possible," said King. The handset is free with the contract - at least for an unspecified launch offer period. Users then choose a mobile package - either 250 or 700 minutes of mobile voice - provided by the ("MVNO") deal BT has with Vodafone.

Users then choose a data package, again over the mobile network. 1 MB of data will cost £39.50 per month on the 250 minute voice package, or £60.50 with 750 minutes. Unlimited data costs £54.50 or £75.50 respectively.

For the VoIP option, BT offers free calls to UK landlines, when the phone is connected to WiFi, a feature which could be useful abroad. It should connect free - for VoIP only - at BT Openzone sites, and be able to connect to office or home WiFi, as well as to other hotspots, which will add a fee.

To do data over Openzone, users can add a subscription giving them 4000 minutes of WiFi for £25. Users can also migrate to the package from BT's business email package, and can add the package to BT's Business One plan.

With other providers doing push email with broadly similar prices, and also offering the HTC S620 (for instance as Orange's SPV E600), WiFi and VoIP are BT's major distinction. At this stage it looks like a relatively minor part of the package, but in future, we can expect the company to move traffic towards WiFi where possible. Since BT has no mobile network of its own, it makes less money on the mobile part of the deal - provided by Vodafone, and has an incentive to move traffic off the mobile network, unlike other providers - even T-Mobile, which has its own hotspots.