Hey,
to my knowlege a special controler for only efects is new for me

. But you can use nearly every MIDI controler at DVS. Some of them (the most popular devices like Pioneer, some Numark controlers) are pre-mapped so you have only to select the mapping to work with the controler. If you buy an controller which is not in the list:
http://www.mixvibes.com/content/support/dvs-ultimate/dvs-ultimate-articlesthere you have to open the "MIDI presets in MixVibes' softwares" to get a list of the pre-mapped devices.
Alternative you can look at your preferences at DVS at the MIDI section and look in the list there.
If you want an controler which is not in the list you have to map it yourself. There you can use auto-learn function (works for 80% of the buttons) some of them you have to map by hand.
If you have some futher question don't hesitate to write again.
regards
Christian