That's a very good idea (scanning from 3rd machine). I'll try that as soon as I have the ADSB device with me again (it's currently in the a/c at the airfield).
I thought about trying ad-hoc mode, but from what I could see, iOS did not support it.
However, I just searched a bit more, and I get conflicting results - it might be supported after all.
I'll park this for a few days until I have the ADSB device with me again.
Thanks for all your help & ideas - that's awesome - I now have a few new avenues to explore, which makes me happy!