Digital hide and seek

"Dodgeball" is a mobile phone service that informs you of your friends' locations via text message. In the past two years, about half a dozen Dodgeball competitors have launched, including Loopt, Brightkite and Whrrl. Helping to advance the trend, are a raft of GPS-enabled cell phones. Data for these services are hard to come by, said an analyst at Forrester Research, but he estimated that users total "a few million in aggregate."