Mad Developer lets you do this in a round about way. I DON'T know if PC Connectivity Manager package lets you do this, but if it does, cool. Wouldn't surprise me if it did.

But I agree, a status menu applet would be lovely - all you have to do it replace the existing one with one that uses the scripts Mohammad just posted to switch the USB modules. In fact, I think that's better than adding another one along with the already existing one. Just create a modified version of the current one, and have it replace that one.