The drive toward fixed/mobile convergence is accompanied by a lot of auspicious anticipation over the next batch of applications to be born of that convergence and the added revenue they will bring, but there’s less certainty over exactly what sorts of applications will fulfill those expectations.

In a panel discussion at the Voice on the Net show in Boston this week, Tom Valovik, IDC’s VoIP infrastructure program director, posed to a range of industry experts what he called “the 15-year-old teenager question,” which asks one to explain to a hypothetic 15-year old the sorts of gee-whiz applications to be engendered by converged fixed/mobile networks.

A representative from Sprint Nextel imagined a smart video-enabled handset using unlicensed wireless broadband to attend a class remotely, even getting questions answered by the professor. Someone from Ericsson suggested mobile video chatting. Another Sprint Nextel executive volunteered that she didn’t have any teenage kids--only a teenage cat. And another panelist, from Lucent Technologies, admitted having neither kids nor cats.

An application developer in the audience then stood up and mildly reproached the panel for not offering much in the way of inspiring ideas for new applications, to which the Lucent executive replied that it’s not fair to put people on the spot like that, since most people can’t dream up new applications on command.

In another panel discussion two days later (entitled “Cool Applications,” in fact), Liora Bram, director of mobile applications marketing for NMS Communications, seemed to defend the notion that cool apps are unpredictable.

“Ringback tones took off,” she said. “No one knew that was going to happen.”

Her colleagues on the panel, however, were more than willing to take a stab at describing the cool apps of the converged network.

Jeff Liebl, vice president of marketing for Ubiquity Software, imagined a technician in the field using push-to-talk to contact his supervisor through her PC, telling her that a particular part is needed. After mutually consulting a supply database, she conferences in a parts supplier who is also in the field and dispatches the supplier to the technician’s location.

Steve Blumenthal, Bridgeport’s chief technology officer, envisioned a businessman with a bluetooth-enabled laptop and a presence-aware mobile phone. While he’s at his desk, he uses his office softphone, but when he walks out the door, the bluetooth system senses that he’s left and activates his mobile phone, forwarding calls to his mobile as he sees fit. When he returns to his office, the system senses his presence again, disables his mobile phone and sends all calls to his desktop softphone again.

At press time, no 15-year-olds were available for comment.