Nokia has updated the OS (operating system) for its Wi-Fi internet tablet device, adding support for VoIP (voice over IP) and IM (instant messaging), the company said today.

The latest version of the software for Nokia's 770 tablet supports SIP (Session Initiation Protocol)-based VoIP clients and comes preinstalled with Google Talk. The OS, based on Linux, also supports IM clients based on Jabber, an open-source IM platform.

The software includes a full-screen keyboard that users can type on with their fingers, and Google now comes as the default search provider on the device.

Nokia said it added the features based on customer feedback. The number-one request was for VoIP support, followed by requests for IM and better input methods, Ari Virtanen, vice-president of convergence products for Nokia, said at the VON Europe conference in Stockholm.

The OS will become available during the third quarter.

Nokia introduced the Nokia 770 last year. It ran on a Nokia implementation of the Linux tablet OS. While Nokia has said the device is selling well, it has also refused to give sales figures. The device has similar features to recently launched products based on Microsoft's Origami design but at about a third of the price.

In a departure for Nokia, which is best know for developing products for the mobile phone industry, the Nokia 770 doesn't come with built-in mobile network support. Instead, it has Wi-Fi, although users can connect their mobile phones via Bluetooth to use a mobile network to reach the internet. "Users are likely to prefer a high-speed LAN," Virtanen said.

The addition of Wi-Fi to Nokia devices has been met with mixed reactions from operators, said Mikko Salminen, director of marketing for fixed-mobile convergence at Nokia. Some mobile operators see Wi-Fi as an opportunity to sell more mobile access, while others see it as a threat, he said.