In theory having an umbrella that can play music would be nice, especially with clever touches like fast forwarding and rewinding by twisting the handle. But think about it… how long do you ever hold an umbrella open at any given time? Enough to listen to one song? Maybe two or three?
Furthermore, I might just not know how to use umbrellas or just have a habit of buying the cheapest and crappiest umbrellas available, but I go through the damned things like you wouldn't believe. It doesn't seem like the most reliable place to stick fancy electronics. I'll just keep my iPod, thanks very much.