In both business and consumer markets, widespread adoption of Voice over Internet Protocol (VoIP) depends on the availability of wireless VoIP handsets, reports In-Stat. Dual-mode cellular/WiFi handsets will be the key driver to mass consumer adoption of VoIP, the high-tech market research firm says. By 2009, In-Stat forecasts that over 66 mln cellular/WiFi handsets will be in operation. Worldwide, consumer VoIP subscribers using wireless IP phones will grow from 2% currently to 73% in 2009. Based on competition from mobile carriers without wireline operations, Europe will be the largest initial market for dual-mode smartphones. While mass production of dual-mode sets is not scheduled until 2007, an In-Stat market survey found that over 80% of businesses have an interest in the technology.