Participle

Participle is an asset that makes it easy to script creative and novel behaviors for particle effects. At its core, Participle is a flexible event dispatcher that offers convenient access to the state of individual particles within Unity's Shuriken particle system. It makes it simple to construct effects that respond to fundamental events, such as particle birth and death, as well as more sophisticated conditions like the length of time a particle has lived or the distance it has traveled.
Participle offers a custom inspector that makes setting up basic and conditional trigger events straightforward. It also offers a full featured programming API.
Features:
Built-in event triggers - Birth, death, time lived, distance traveled, remaining lifetime, size, distance to transform, every frame.
Event trigger modes - OneShot, Repeat, RepeatByIncrement, RepeatByDecrement
Custom event triggers - User specified evaluator to determine the conditions that will cause an event to be dispatched.
Particle attachments - Built-in support for causing game objects to follow individual particles.
Client data - Store and retrieve arbitrary application data on a per particle basis.
Comprehensive API - Create and remove event triggers from code.
Complete documentation
Lots of examples.
Cogent Whir Web Site
Participle Documentation
NOTE: Creating event handlers to be used in conjunction with Participle's event dispatch requires scripting. These scripts can be as simple as a few lines of code or much more complex, depending on what you want to accomplish. The package includes many examples that can be used as is, or as templates for constructing your own event handlers.