For more on these products, including some great videos, check out these links.
Native Instruments Maschine MK2
live performance video
http://www.native-instruments.com/#/en/media/?t=Media&f=mediatype:videos|youtube&content=2125IK Multimedia
a dozen iRig MIX videos
http://www.ikmultimedia.com/products/irigmix/index.php?pp=irig-mix-videoNovation Twitch
three videos – using Twitch with Serato Itch, Ableton Live, and NI Traktor
http://us.novationmusic.com/twitchNumark N4
intro/overview video on YouTube
http://www.youtube.com/watch?feature=player_embedded&v=incah65FrFcSound Trends Meta DJ
Harmony Central video from Musikmesse
https://www.youtube.com/watch?v=qlbTKLNJu0QStanton Scratch DJ Academy MIX!
download free trial version
http://www.stantondj.com/mix-software.htmlDangerous Music Source
product landing page
http://www.dangerousmusic.com/source.html