The Mgic Button site says that it can be mapped to an application button, however I haven't used it in quite some time so it might not work as I am thinking.
Some apps I can think of off the top of my head are iLauncher, Pocket + and Wisbar Advance. Of course these are all commercial software but they do some other things that may make it worth the price for some.
I can't think of any other freeware at the moment but I keep thinking I saw one before.
Anyway, your way is good too.