The amazing Sony HVL-F58AM – bends every which-way to get the bounce light you need. A very powerful flash designed for the Sony A900 flagship camera. It will also work with the A200, A300, A350, A700. It may also work with older cameras but I have no confirmation on that.
If you want a wireless controller for the A900, this is the flash you need.
Sells new for $500.