Replace New Year's Eve Fireworks with an App

There have been some calls for new year's eve fireworks to be cancelled in Australia, due to bush-fires. Perhaps they could be replaced, at least in part, by spectators' smart phones. The idea would be to have each person hold up their phone, which would display part of a coordinated pattern. This would be similar top the effect where those in a stadium hold up colored cards on cue, but could form a much faster changing, more vibrant pattern. This could supplement laser light shows and displays projected on buildings. This would also turn people from spectators, into active participants in the show, as well as avoiding setting off pyrotechnics during a total fire ban.