Who is doing it: Voice over IP has been around for years, but many businesses, especially those with aging telephone systems, are giving the technology a first look. Gary Kuyper, CIO with Bethany Christian Services, likes how easy VoIP is to configure as well as its plug-and-play capabilities. Kuyper is piloting Switchvox, a VoIP system based on Asterisk open-source tools. An adoption and foster-care organization, Bethany has 80 offices and another 20 to 30 telework locations. VoIP would allow Bethany to more easily employ untethered workers, Kuyper says, and to serve new locations cost-effectively.\n \n How it works: Because VoIP runs over data lines, IT staff doesn\u2019t have to run separate phone wires to employees\u2019 desks, observes Paul Liu, CIO of Freeborders, an outsourcing vendor considering VoIP. \u201cThat goes directly to the bottom line.\u201d Meanwhile, employees can plug in their phones anywhere they have a broadband connection and their numbers will follow them.\n \n Growth potential: Residential and business customers spent $41.6 billion on VoIP in 2009, according to In-Stat, which predicts that 79 percent of companies will use the technology by 2013. Erik Bratt, vice president for marketing at TelCentris, a VoIP provider, expects sales to double in 2010.