Via ,Fab, Topiary is a a tool for prototyping location-enhanced applications. It allows you to carry out wizard-of-oz experiments, with a really good touch.

Topiary lets designers create a map that models the location of people, places, and things; use this active map to demonstrate scenarios depicting location contexts; use these scenarios in creating storyboards that describe interaction sequences; and then run these storyboards on mobile devices like PDAs, with a wizard updating the location of people and things on a separate device.

Topiary allows designers to quickly design, prototype, and test a location-enhanced application without requiring them to implement the application or deploy a supporting infrastructure, enabling them to get early feedback about their design from real end users.