Digiterra can handle OmniStar Corrections and can display the accuracy information, etc in the GUI
DigiTerra Explorer contains integrated configuration settings to OmniSTAR only for Trimble receivers (http://www.digiterra.hu/wiki/en/downloads/DigiTerra_Explorer_v6_RefGuide/trimble_gps_settings_tab.htm). The only thing you need to configure your receiver to use OmniSTAR corrections with the manufacturer's on-board software than send the positions in NMEA 0183 format to a serial COM port. We have no built-in support yet in the software for other receivers in terms of OmniSTAR.
Replying to the second half of this question: our software is able to display (http://www.digiterra.hu/wiki/en/downloads/DigiTerra_Explorer_v6_RefGuide/index.html) and to capture horizontal and vertical positioning errors (watch the video tutorial)