Mai has a cool idea: "Postulating that the ideas of perceptional stimuli and emotional stimuli can be combined à la Synthesia, brings up the idea of a (fantasy) phenomena that I've been thinking about."
When I first read Blue Cats and Chartreuse Kittens I thought synesthesia would make a great condition for a character in a novel or movie. In my version, the character would be a strung out secret agent on the run who hears violins when he sees blood but Mai's version sounds more upbeat like a iPod commercial.
What if iPods had a setting that allowed you to hear what other people were listening too when you got close to them on the subway, etc? Like the way iTunes is networked at the office but out in the wild instead. That'd be neat.