BD3D has released Scatter, a new add-on for Blender for parametrically distributing instanced geometry . It works by automating the creation of a complex modifier stack behind the scenes and offers the user a simplified interface for scattering grass, ground cover, trees and more. 

Features include the ability to create biomes from multiple layers, the ability to set specific densities, batch changing settings, multi-layer painting, path-based distribution, camera-culling, support for its own custom proxy system, and more. 

Scatter costs $60 and includes several presets. Learn more on Gumroad.