There is also the Genesys XP from Generalmusic which, like the Midjay, can play MP3's, Audio CD's, Midifiles, Styles and sounds. It is larger and more expensive but offers much, much more sophistication in it's sequencer, synth editing and full blown style creation.
Also, Yamaha makes the QY100 which although does not feature single fingered chording, it is an arranger module and XG sound module with a mic or guitar input. You must play 3 fingered chords to trigger the styles within the module and because it is very small, there are very few arranger function buttons like the Genesys.
Kaye's Music Scene