thanks for the link, but no. it's not compatible.
it does what i need, but unfortunately doesn't do it for the MX900. $20 is a little steep too!
so, i decided that since i don't travel much, the RF wireless StudioMouse would be a better replacement for my wired StudioMouse. i'm returning the MX900.
also, i'm getting the black/silver version of the StudioMouse, since the white sides of my old one get dirty from use.
by the way, i asked kensington when they were going to do a Bluetooth StudioMouse, and they basically said they might have one soon. so i'll sell the RF version when that comes out.