Applied to the Swift it was an enexpensive mod. Cost me no more than $5 ro $6 plus some minor parts readily available.
Not too many people were interested - the biggest objection being "if you don't use flaps it doesn't help." Correct. However, in my own case it is a rare - really rare - landing I do not use flaps.
Below is a drawing of my flap/gear warning system which I consider a MINOR alteration and requires only a log book entry by an A&P.
Buzz Winslow