Korean Con&Com offers Karaoke systems inside microphones with SD card slot.

The times are long gone, where you needed a big tower of components for Karaoke. Several karaoke systems are available that are integrated inside the microphone. Back in 2005 Panasonic introduced as far as I know the first Karaoke microphone with SD card slot.
The Con&Com Munia MH-6600 Karaoke microphone supports SD cards up to 2GB and also has a complete button field to remote control the karaoke functions. The MH-6600 supports DivX and MPEG1, 2 video playback and mp3 music playback.
The firmware can be upgraded via a SD card.

Other features include various volume controls (Echo/Chorus/Accompaniment/Microphone), tempo, pitch and key change functions and rhythm change.
The company offers a catalog of 100,000 songs and new songs can be downloaded via the net.
The MH-6600 has to be connected to a TV via a cable. Con & Com also offers a wireless karaoke system dubbed Munia MR-9100 (see photo below).
The Con&Com karaoke products seem not to be available in the US yet. Via the Con&Com site.