Let me try and give some steps to get bluetooth sync working with Missing Sync. I have a Dell Axim x51v running Windows Mobile 6, a Macbook Pro running Leopard, and Missing Sync 4.0.2. I can't claim that this will work with anything else, but hopefully it will.
I'm assuming that a profile has already been created for Missing Sync with your device and that it syncs properly, either by USB cable or some other means.
Let's begin with bluetooth on Leopard.
1. Ensure that bluetooth is enabled
2. Make your computer is discoverable by bluetooth. Click on the bluetooth icon on the menu bar and ensure that there is a check next to "Discoverable."
3. In Missing Sync, ensure that sync by bluetooth is enabled. Click on the preferences button on the toolbar, and in the "Connections" section, ensure that there is a check next to bluetooth.
Now, on your Windows Mobile 5 or 6 device:
1. Turn bluetooth on. From the Today screen, click on the bluetooth icon on the bottom right hand corner, push on the mode tab, and check the box next to "Turn on bluetooth." Push OK.
2. Push Start -> Programs -> Activesync.
3a. In Activesync, push Menu -> Connect via bluetooth. If the device has been previously paired with your Apple computer, it should connect to Missing Sync and sync normally.
3b. If your device has not been paired with your computer, you will get the following message: "Cannot find an existing bluetooth partnership with a PC that supports ActiveSync. Would you like to set up a partnership now?"
3b1. Push Yes.
3b2. This will bring you to the Bluetooth manager under the "Mode" tab. Ensure that bluetooth is turned on by the checkbox being next to "Turn on bluetooth."
3b3. Push on the "Devices" tab.
3b4. Push "Add new device..."
3b5. It will search for bluetooth devices. Your computer should show up in the search.
3b6. Select your computer and push "Next."
3b7. Enter a passcode. (I use 0000). Push "Next."
3b8. A dialog box will popup on your computer asking for the passcode you just entered on the device. (In my case, 0000)
3b9 . On your device, it will ask you to "Select a service to use from this device." Ensure there is a checkbox next to "Activesync."
3b10. Push Finish. Your computer should now appear in the list of paired devices. Push OK.
3b11. Open Activesync (Start -> Programs -> Activesync)
3b12. Push Menu -> Connect via bluetooth.
3b13. Viola. Missing Sync should appear, and you should be able to sync as normal.
I hope this helps. Let me know if you run into any problems or if something is unclear.