Mode S receivers
Curious Pax, the Kenitic SBS-1 one users who used to feed to a dutch site appeared to have defected to an american site owned by a company called Air Nav systems. they now sale a a S mode receiver called an Air Nav Radar Box which produces a radar screen on your PC. It costs £40 less than Kenetics and they appear to have far many more users who are streaming.
I have been informed that the axact location and time above a point is not perfect to stop the stinger pointing baddies from using it to shoot down aircraft. The system looks good for general use, though I suspect that if you live near an airport or airways junction then you may find it in accurate on purpose.