Waspmote Smart Parking

The Waspmote’s Smart Parking Board principle of operation is based on the variation of the magnetic field above the board caused by the chassis of a vehicle placed on the parking lot where the mote has been deployed. This change is detected using a permalloy magnetic field sensor (MFS), a material whose electric resistance varies with the magnetic field through it, measured and processed to provide the system with an answer that can be used to determine the state of the parking spot.

Documentation:
Waspmote Quick Tutorial
Waspmote Site 
Waspmote Technical Guides 
Sensor Boards Technical Guides 
Networking Guides 
Developers Forum 
Videos 
Articles 
50 Applications with Waspmote 
FAQ: Waspmote Vs. Arduino