Just was searching the forum for VRPN info for VVVV and saw that there was a request back in 2011 for implementation of VRPN in VVVV.
Just want to say how I got it working.
I found .net bindings for Vrpn
It worked out of the box with the provided dll in a plugin. See the printvals example in the vrpn source for infos how to implement it (it`s really easy).
My problem was that I was in need of a other vrpn version, so I had to recompile VrpnNet with another version of VRPN, it was really hard to find the source of VRPN (the old releases) but I found them on an ftp server: ftp://ftp.cs.unc.edu/pub/packages/GRIP/vrpn
After recompiling VRPN.net to the right version everything is working great.
With VRPN you get alot of devices working without programming a plugin
See Trackers on Page Redirection
Good thing about VRPN is that you request data from the server, so you don`t have to worry about framerate and stuff.
We used Optitrack within vvvv using their NatNet .net library, it was pretty straight forward (sample code is part of the download which can be rewritten as a node quite easily)