Verizon Wireless is already testing a ringback tone
service right now in parts of California, but we just got a hot tip from a highly reliable source that T-Mobile has
"imminent plans to announce a nationwide ringback service" of their own. T-Mobile had no comment when we asked them
about this, but they didn't deny it, either.
P.S. - In case you aren't familiar with ringback tones (and believe us, you will be very soon), they're basically customized audio clips that callers hear when they dial your number instead of the usual ringing sound.