> Simply holding the watch’s built-in speaker up to the receiver of a push-button telephone allowed users to place calls to stored numbers
So a miniaturized version of one of this (which I totally uselessly had as a kid): https://www.youtube.com/watch?v=z438yRW0rGQ.
https://phonelosers.com/redbox/tonedialer/
https://hackaday.com/2014/09/05/radioshack-phone-dialer-red-...
And now that you remind me, that's totally why I bought one, but at the time I lacked the tools and electronics skills to do the mod.
> Simply holding the watch’s built-in speaker up to the receiver of a push-button telephone allowed users to place calls to stored numbers