Basically said, no, haven’t heard a peep. I think they are missing out. Such an element—hover triggering sound and a visual change—would add a lot of pizazz and art to their app.
I did something like this to make a little app (fit on a floppy disk) called Sound Toy. Won the New Visions/New Voices contest in 1994 sponsored by WIRED magazine and Voyager Publishers. Used a now dead visual app builder called, I think, Sirius App Builder. Been on the lookout ever since for something to bring my Sound Toys concept to the online world.
Please tell me if you come across anything.