CED2911 released a port of SMS Plus, an emulator for the Sega Master System and Game Gear consoles, for Xbox 360 systems to use with the Xell JTAG Hack (right now just available for Xenon/v1 360s). The author also announced next he’ll be working on a genesis/megadrive emulator.
SMS Plus is a freeware, open-source, portable emulator for the Sega Master System and Game Gear consoles.
v140909a: Fixed controller bug
Thanks to http://www.tehskeen.com/forums/showthread.php?threadid=13929 for the news.