You could emit objects from a vertex group of a ico sphere. Let the emitter follow a curve a force field could follow the emitter and attract all particles. The distance of the force field can be controlled by offset.
The fade out of the trail can be controlled by the particles age e.g.
http://blend-exchange.giantcowfilms.com/embedImage.png?bid=893
(Note that the particle count has been lowered in the .blend) The age is not correctly calculated when using child particles.
