PORT-AU-PRINCE, Haiti—Chasmaille Odera was so obsessed with writing instant messages on her white BlackBerry, the 20-year-old host of a music-video show here decided to write her own song about it.

"Map Chat," released earlier this summer under her stage name, Shassy, quickly spread through popular radio programs, local DJs and online. It now blares from car stereos and bars along the capital's streets—the latest anthem to Port-au-Prince's love affair with the BlackBerry and its instant-messaging service, BlackBerry Messenger,...