WoW:API GetUnitSpeed

This is a work in progress...

When the unit is not moving this returns 0
When the unit is on a moving object such as a boat that's moving this returns 0
When the unit is running at 100% (running on foot with no speed increase enhancements) this returns 7
When the unit is running at 175% (Death Knight home city) this returns 12.25

Still figuring out the relation between the speed and the value returned.