There is a Bluetooth toggle (sorta) already on the homscreen, the upper right most corner of your homescreen is a quicklink (on OS 5.0) to Manage Connections, where you can toggle, bluetooth, wifi, and your cell connection. You can scroll to it with your trackball, or trackpad, OR just click on that part of your screen IF you have a Storm 1 or 2.
Also if you have the app Quicklaunch, you can put a bluetooth toggle on it's menu.