BG Micro is selling a SonaSwitch Mini S sonar distance sensor for $9.99 and I just picked one up. For $9.99 you get a Polaroid instrument grade transducer, mounted on a same-sized board that gives two open collector outputs, one triggers at 5ft, one at 7ft.
SonaSwitch has another unit that looks identical, but gives an analog output to indicate distance. I picked this up thinking either I would have a cheap transducer, or possibly there would be a way to hack an analog output out of this, if it's the same PC board on both units.
So the package just came. Has anyone tried this already ? No sense duplicating effort ! :-)
-Chris