Ed S schreef:
I searched around a bit and couldn't seem to find any talk about an
opensource implementation of ADS-B (and maybe some open hardware). Has
anyone heard of such a project?

It sounds like a worthy project to keep the prices from Garmin and the
like in check so a opensource applications can be written to use
utilize the underlying ADS-B implementation.

What's ADS-B? A US term for a mode S transponder?