The Wondermega is a combined Sega Megadrive and Mega CD manufactured by Sega and JVC, that also features a DSP for audio enhancement, MIDI out, two microphone inputs and a S-video output. Well, at least Wondermega mark one does and its a mark one that's been put up for auction over at eBay. Here: Sega Wondermega.
Interstingly and unlike the CDX, the Wondermega is compatible with the Sega 32X and even had the Wonder CD peripheral released for it.
As for the particular Sega Wondermega on offer, it is in very good condition, comes in its original box, but lacks the 110V power supply. Seller ships worldwide.