Hi all,
 I'm using the soundbeam[1] for a project with music
therapy and educational application; it's a great device
with customisable sensitivity, it's possible to get midi
messages from it, connect more than one, etc. On the
other hand, it costs around 2000€. Is there anything
out there that uses the same principle (a sonar beam
to get your position) or works in the same way but
which costs less? If open source, it would be even
better.

As always, thank you all!
--
Marco