British carrier O2 has today launched a new VoIP and messaging service called TU Go, which is available to its pay monthly customers with Android and iOS devices. The service allows users to make calls and send texts over the Internet, so even when they have no cell reception, they can connect to a Wi-Fi hotspot and get in touch with friends and family.

TU Go is similar to Skype’s paid calling service, but because its an O2 service exclusive to O2 customers, it doesn’t require a separate account. All calls made through TU Go are charged to the customer’s bill at the standard call rate — they’ll come out of your minutes just like standard calls and texts — and they appear as if they’re coming from the user’s cellphone number.

The best thing about TU Go is that it doesn’t have to be used on your O2 phone — you don’t even need to have your O2 phone with you. You can use it on your iPad, an Android tablet, and even your Windows 7 computer, and it works in exactly the same way — all you need is your O2 number to activate the service.

So you can make and receive calls from your PC while in the office, and they look like they’re coming from your smartphone — isn’t that great?

The only limit to TU Go is that you cannot be logged into more than five devices at any one time, but who’s going to need more than that? Also, there are no TU Go apps for Mac OS X, Windows Phone, or BlackBerry just yet. We’re hoping, however, that if the service is well received, these will come in due course.

If you’re an O2 customer, you can download TU Go now from the App Store for iPhone and iPad and from Google Play for Android.