Precision blade balancer for modeling propellers of all types and sizes - from lightweight for slow-flyers to large wood or carbon for giant models. The only limitation - the hole in the propeller must be less than 15 mm.
Wind speed and direction meter for use with a smart mobile phone equipped with a magnetometer and digital compass. Supported iOS7 and above and Android 4.0+. http://vaavud.com/blog/posts/so-how-exactly-do-they-work