One of the design features of the Cessna 150 that I admired most is the
stall warning. It is a small aperture in the lower curve of the leading
edge guarded by a wire screen (those pesky flies!) The cavity connects
to a tube leading to the wing root in the cabin. There, covering the
other end of the tube is a mouth organ reed, arrange to be silent when
blown, and to whine when sucked. That's three components and just one
moving part if you could call a vibrating reed, a moving part.....
The most bang from the least buck - it seems to me.

It was pre flight checkable - with a wipeoff of fly squash and a mouth
applied suck. Wonderful!
It was not everyone's cup of tea, I don't suppose: in particular, that
mouth to wing actvity was eliminated by a small vane on a microswitch,
which howled when the vane pushed up at high AofA. I think that was a
C172 mod wasn't it? It needed power to work though.

Anyway, for something a little fancier yet, a kind of lift reserve or
AofA indicator that takes two pitot tubes to a differential pressure
gage, shown he about $`125

http://www.pipcom.com/~cowcam/AOAr.htm

I am prejudiced in favor of red sector in right, not in left but that's
just my feeling.

[No financial interest]

Brian Whatcott
Altus OK