(FORTUNE Magazine) – Reaching a live person on the phone and winning the lottery often seem to carry similar odds. But all that may change if wireless business phones meet their much vaunted potential. The idea is that you can dial one number and reach the person you're calling, whether she's at her desk, in the corporate cafeteria with a portable phone, or even wandering about the country. So far only about a hundred large U.S. companies have installed such systems. Jerry Kaufman of Alexander Resources, a telecommunications consulting firm in Scottsdale, Arizona, says the market, which includes equipment sales, installation, and usage fees, will reach $20 million this year. Some, like AT& T and SpectraLink of Boulder, Colorado, are installing basic cordless phone systems like the ones you use at home. Cellular providers such as the Baby Bells, McCawCellular Communications, and Sprint are taking a different tack. They fit office buildings with antennas so cellular phone signals can travel indoors. (Today's standard cellular phones suffer from poor reception inside buildings.) Southwestern Bell recently patched financial service giant USAA into its cellular network so that workers could carry and use their phones anywhere in the building. This was no mean feat: The company's San Antonio headquarters is the largest private office building in the world -- three- quarters of a mile long and five million square feet. -- J.M.