ADSB tracers
I received, as a splendid gift, an AirNav RadarBox.
You install the software, plug in the little black box and the little antenna and voilą ! On your screen, in real time you can see all the airplanes that are transmiting ADSB and/or mode S.
Automaticaly the software interogates online database and provide you with pictures of the airplane. You know it's altitude, registration, origin and destination. It's a splendid device. One option is to share the data you receive online with other users. In that case, the data is delayed by five minutes . Apparentlly an international consensus for security reasons.
You can set specific alarms. I am therefore informed by email when certain registrations are detected.
I don't feel that I am a danger to anyone when using it. I enjoy it so much I got a second screen for my computer and the device is running all day long on it's dedicated screen...