The Mustek's gsmart has the ability to make short video-clips.

The file generated is an .avi file, using a codec/decompressor indentifying itself as SP54. The codec will usually be installed by default when you install the bundled software.
Apparently a form of MJPEG but with some internal information missing.

Hardware using this format:

Aiptek's Pocketcam digital still camera

Logitech's ClickSmart

Mustek's gSmart mini 2

The 'SP' could mean 'Sun Plus', as those hardware use this type of chip.

The only FOURCC really used by this codec seems to be SP44.