From the December 2004 issue of Entrepreneur

The dream is a world where phones and other mobile devices seamlessly hand off your calls according to the availability and speeds of different networks. Integration of services like VoIP will not only create more flexible work environments, but could also save you money by transferring calls to the least-cost network.

Making this a reality requires cooperation between cellular service providers, software developers and hardware manufacturers. The first hybrid device debuted this fall, focusing on data rather than voice services. Hewlett-Packard, with T-Mobile, recently brought out the $499 (street price with activation) iPAQ h6315 Pocket PC. Stocked with Bluetooth, a removable keyboard and an optional camera, it can hop from a cellular network to faster Wi-Fi for data transfer when available.

Nokia has developed a phone with similar capabilities for the European market. But don't expect U.S. cellular carriers to rush in; they're still figuring out how to generate revenue and manage billing for these services. The exception is T-Mobile, due in part to its network of Wi-Fi hot spots. Expect advances in 2005.