The Canard Aviation forum had a quick heads up about this product:

http://www.zaonflight.com/http://www.zaonflight.com/

Two models of passive traffic detection that are similar to existing
ones: Using the "local" transponder as a benchmark for gauging distance
from other targets.

One model, however, has what I am assuming is a phased array antenna on
top that permits ROUGH bearing detection as well. SO, if I read the page
and specs right, this gives approximate distance, relative altitude
based on Mode C, and approximate bearing (to 30-45 degree resolution) to
multiple targets.

Anyone seen a trade pub review yet on this device or know anyone with
hands on experience to share?

The bearing info is damn near a clincher in my eyes... given that its a
lot cheaper than Mode S and a TIS display, and can give info outside of
the TIS area. Nothings perfect.. but this is better than whats out there
now (in passive detection.... on paper that is).

Dave