Voice over IP (VoIP) technology lets you use your Wi-Fi enabled PDA or smartphone to make phone calls over a wireless LAN (WLAN), home or work, or at a hotspot; found at your local Starbucks, Borders, and in some cases, even McDonalds, etc.

To many, however, the true benefit of VoIP lays in the promise of seamless dual-mode (cellular and Wi-Fi) roaming or convergence. For example, step out of range of a WLAN during a VoIP phone call and you're automatically switched to your handset's GSM or CDMA radio.

Convergence also promises to deliver voice or data over the type of network that is cheaper, more optimal and, of course, available at a particular moment.

For instance, say you're talking to a friend on your smartphone while walking down the street. Enter a café with a Wi-Fi network, mid-call, and your mobile handset automatically switches to a VoWLAN connection, saving precious minutes and money in the process.

A number of companies and organizations have announced plans to help make Wi-Fi/cellular convergence and straight VoIP phone calling from handhelds more widespread.

Boingo Wireless, VoIP service provider Ecuity, and software-based phone maker Telesym are in the process of choosing people to test a new service for making calls from any of Boingo's 13,000 hotspots via a Wi-Fi enabled Windows laptops or Pocket PC Phones and PDA.

Research In Motion (RIM) demonstrated its first handheld in years to do without a cellular component last fall. The BlackBerry 7270 can still make phone calls and exchange data, but instead of using a GSM or CDMA network, the new handheld accomplishes this through Wi-Fi.

Although RIM is still beta testing the 7270, it recently announced partnerships with 3COM and Nortel Networks to separately provide underlying technology to enable VoIP for the handheld.

Motorola and Skype will work together to develop VoIP connectivity options and access for Skype users on Motorola devices. The companies plan to co-market some Wi-Fi enabled Motorola handsets as Skype Ready, with the first such products expected to be ready during the first half of 2005. Perhaps that's why it has taken so long for Motorola to release the much heralded MPx Pocket PC Phone in the United States?

Wi-Fi Alliance is in the process of adapting its certification methods for the needs of the cellular industry, as a number of new or upcoming smartphones combine Wi-Fi with cellular technology. To do so it created a Wi-Fi/Cellular Convergence (WCC) task group to determine that industry's certification requirements for Wi-Fi functions.

Devices already certified or in the process of gaining approval (as of last October) include Hewlett-Packard’s iPAQ Pocket PC h6315, Nokia's 9500 Communicator, Motorola's aforementioned MPx, Intermec's 760, and SanDisk's Connect Wi-Fi SD card. The Wi-Fi Alliance used its Application Specific Device program to okay these handsets.

Last fall 14 companies announced the publication of the Unlicensed Mobile Access (UMA) specifications for extending mobile voice and data services over fixed wireless LANs. The goal of UMA is to let consumers roam seamlessly between their cellular networks and the wireless LANs in their homes and offices with dual mode mobile handsets, such as those mentioned above.

Carriers benefit through the capability of delivering their same services—voice, data, SMS, downloads, etc. over another type of network, Wi-Fi, in parallel to their traditional cellular networks. To compete with VoIP services, operators could offer limited or unlimited WLAN access for a fixed rate.

One mobile handset that will deliver on the promise of convergence is Motorola's CN620 Dual-Network Mobile Office Device. Announced back in July 2004, the CN620 is the result of a collaboration between Motorola, Avaya, and Proxim.

Avaya and Proxim provide the WLAN infrastructure equipment to support Motorola's mobile handset. Because the CN620 is part of a larger platform, you won't be able buy the device and have it seamlessly switch between a Wi-Fi and cellular network if the WLAN is not part of the enterprise with which it is deployed. So no public hotspots or WLANs at home for the CN60.