I have also used them in wind up machines.
CAVEAT: These needles sound great and last a very long time. I've used them for 78s, Victor Program Transcriptions, and 16" early transcriptions with success. That said, if your wind up or electric machine has a heavy pickup like a horseshoe magnet type, I'd do due diligence first- select a Columbia Viva tonal or OKeh Electric laminated disc that you don't like and isn't worth anything for a Guinea pig. Play it a few times and if it doesn't show wear or change color perceptibly you'll be OK.
Also- I have no idea what the "It Retracts!" gimmick is all about. I've never been able to make one do it or seen one do it. Google doesn't seem to know either except for one post about them on Worth(less)Point that claims the jewel "floats" in the shank:
http://www.worthpoint.com/worthopedia/n ... needle-100+
I think their estimation of number of plays is pretty accurate, though. They normally last 6 months or better for me- and I play records a lot!

Price is $20 each or 6 for $100. I probably have at least 50 of them so stock up if you are into early changers!