Stall Warning Indicators and Your safety

Reading that many lethal accidents are caused by stalls I thought that
a stall warning indicator might be a nice thing to have. After
searching a bit I found this really interesting but sad story on the
subject written by someone at DG sailplanes:
http://www.dg-flugzeugbau.de/ueberziehwarnung-e.html

In it he mentions several significant points: Any experienced pilot
can and will stall the glider at some point. He even admits he has
done it and had a hard landing that cost him $8K in repairs! Humans
make errors!
Modern sailplanes are so clean that they give very little clue before
stalling.
I did a search for such a device. Found some very expensive devices
for general aviation and one device (Redding) for $90 that is just a
microswitch with a vane that requires cutting a hole in the aircraft.
Ugly.
Being an engineer I can envision a simple, cheap (~$200) device that
is "smart", can be automatically switched off at altitude or manually
switched off if you like to thermal below minimum sink (why?) or for
whatever reason, to reduce the annoyance factor.
It could require no panel space other than a switch or knob, run on
12V and tee off the line to your airspeed indicator. It could be
programmed to give warning beeps when approaching a stall slowly or
continuous tone if approaching rapidly.
I'd like to hear pilots thoughts on this idea and if they would be
interested in such a device. For me, I'd rather have something like
this and feel just a little bit less likely to succumb to human error.
Dean