With more people setting-up wireless home networks and more devices offering Wi-Fi, there is a growing rumbling about really taking advantage of these technologies to get the most out of internet telephony. After all, you pay those monthly broadband costs so why not get the most from it? Tesco have had a VoIP service for some time and their latest launch, Talkwi-fi, takes the service mobile.

Talkwi-fi takes advantage of Wi-Fi compatible handsets to give you "free" or "free-ish" calls when you are in a hotspot, most likely at home or at work. The first big stumbling block is that the application currently only supports four devices from Nokia: the E51, N81, E65, N95. That’s no bad thing as these are all decent phones, but it instantly limits the service, but we’ll come back to this point later.

To get the service, all you have to do is send a text to the Talkwi-fi number, which you’ll be charged £1 for, and you’ll get a link in return. A quick download and installation is quickly followed by confirmation and a credit of £1. Of course the service works over Wi-Fi, so you need to make sure your Nokia phone is hooked into your Wi-Fi network. This is also fairly simple with Nokia phones, with a corresponding on-screen icon telling you that you are connected.

Talkwi-fi will appear in your phone menu and gives you a main screen with four main options: Contacts, Messages, Account and Settings. In truth it is pretty much a case of installing and ignoring. It will quite happily sit in the background providing you with a VoIP option whenever you are within a Wi-Fi zone, making it really convenient. Another on-screen icon shows you that you will be using an internet telephone options, to remove any doubt.

When it comes to making a call, simply dial the number you want and you’ll see on the screen that you are using the Talkwi-fi service. Connection, we found, took slightly longer than straight dialling over the normal mobile network. Call quality was very good, the callers didn’t know we were using a VoIP service, although things were perhaps a little on the quiet side. Of course, you need to ensure that your Wi-Fi network is pretty solid before you start, or you’ll keep dropping calls.

A contact list, rather like any other online instant messenger contact list will let you see who is currently connected, or "online". Beware, however, as if that person doesn’t answer your call, you’ll be routed through to their standard voicemail at normal call rate.

So far so good, but what’s the catch? Well, as we mentioned, it is limited to those few Nokia handsets, which is by no means a coincidence as you can get them through Tesco’s own mobile service. Talkwi-fi gives you free calls to other Talkwi-fi users so long as you are both in a Wi-Fi zone, so some tactical planning can slash phone bills between family members or friends.

But Talkwi-fi will also give you calls to mobile and landline numbers, domestic and international, and then the costs start to vary based on your call plan. You can opt for pay-as-you-go, meaning a landline call would cost you 2p per minute, a tenth of the normal pay-as-you-go Tesco Mobile rate, or 10p per minute to mobiles, half the normal rate. This, of course, needs to be considered in the context of whatever talk plan you have with your provider.

Talkwi-fi also gives you instant messaging, so if you spend a fortune on messaging every month, then you could be getting free messages, again between Talkwi-fi customers, although there are other mobile protocols that will let you do this on a wide range of handsets. The biggest challenge is getting your entire social circle to sign-up - which again highlights the biggest limiter here: the choice of handsets. The service is open to all, whatever network you are on, so long as you have the right handset.

Price when reviewed:
dependent on contract

Talkwi-fi is essentially limited in its appeal because the current offering will only be available to a small segment of users. If the service was available on a wider range of handsets, we could see it being very popular, especially amongst teenagers and students, who probably have regular access to Wi-Fi, not much cash and plenty of people to call.

Credit should be given for the simplicity of the service - it works seamlessly and in all our tests, we barely even knew we were using a VoIP service. Looking at the bigger picture you get the feeling that Talkwi-fi launched slightly too early and if there was wider support, then Tesco could have made a much bigger impact in the mobile VoIP arena.

We await the day that wider handset support is offered...