The $2300 Katech Whistler looks like a 1980s microprocessor with a microphone and frequency analyzer soundcard.

Todays smartphones or tablets have the computer chip, microphone and soundcard.

Someone who wants a home business
could write an Android/iOS app,
and supply the low volume air regulator
and whistling sparkplug screw in adapter.
Such an updated package kit could sell for less than $100

I wonder if there is a US Patent Number for the Whistler?