If I remember correctly, Navman are the only company at the lower end of the market (where most of us live) who have the "Track-your- buddy" feature.
Mike, look at the Navman 7200 VHF (7100 or 7200).
Other makes at the lower end of the market allow the GPS and VHF to be connected togeather so that your GPS co-ordinates are displayed on your VHF screen (and hence your GPS co-ordinates get transmitted when you press the DSC button), but I don't think they allow the location of other boats to be displayed on the Plotter screen.
Adam has a Garmin 300x series GPS Plotter (higher end of the market) connected to an iCom VHF. The 300x has the necessary software to display DSC messages on the plotter screen.
I don't know if the new series of "low end" Garmin plotters, which have just been released, support this feature. There's not much information on them on the Garmin web site (can't download a User Manual, yet).
The VHF has to have the connections for NMEA output. Most only have NMEA input connections to allow it to receive the GPS co-ordinates from you Plotter.
Adam's Icom VHF does send NMEA out. However, the Icom M421 (which a lot of us have) does not have connections for NMEA output, so even if our plotters supported the displaying of DSC positions, the VHF could not send the appropriate signals.
My head's a bit screwed at the moment, so I could be talking a load of bolax.
BF