T&T: sea water alarm

[badornato]

does anyone know of a non invasive sea water flow alarm device.  it
seems that it would be easy to have some type of device like
ultrasound  that simple wraps around the hose and lets you know there
is flow. and to be really cool it would send the info wirelessly to
the pilothouse.
and if this doesn exist, was is the best/easiest to install alarm system?

-- 
bruce adornato
kk42 amelia..san francisco