Spectec, based in Taiwan, has released a SDIO video-out card that supports Windows Mobile 5.0 (as well as PPC 2002/2003). It supports resolution up to XGA (1024×768) as well as S-video and composite video interfaces. It also comes with a 10-button remote control unit and an adapter to connect the device to a standard display cable.
A miniSD version is also apparently available but I could not find it on the Spectec web site. Spectec is also planning to introduce a microSD version later.
The card was on display at the Taipei Telecom 2006 show and is expected to sell for about $100 USD.