Yes, you can use your 30 year-old IBM Model M with Bluetooth!
I found the this bluetooth adapter that's made by Handheld Scientific, and it works great with the Model M. Just plug in, and press the button, pair it with your device, and start typing.
I tested this with my Model M made in 1990 by IBM, on my iPad2. The keypad (and num-lock light) and a few other keys did not work, but that's more of an iPad limitation than the adapter. I was able to type for several days to a week on it, which isn't bad considering the high current draw of the Model M. (I have yet to test it with my Unicomp board.)
Negatives, well, you think bluetooth, you think portable devices. The iPad 2 weighs about one pound, and the Model M weighs 5 pounds, so... Also, it's a bit ungainly to carry around a keyboard with a cord, and the adapter at the end of it. None of that, however, is the fault of the adapter.
Overall, I'm quite happy with it, as I can use a real keyboard with my iPad.
Serial Number: 1000002490
Dimensions: 2" x 2 1/2" x 1"
Keyboard ports: 1 P/S2, 1 USB
Charging port: 1 mini USB
Buy Here (Handheld Scientific's website, $39, last time I checked)