The softproof on the monitor is a simulation of chosen standard for proof and print. It needs a well calibrated and profiled monitor. For a high-quality softproof the monitor should deliver the possibility of hardware calibration. In this case the monitor itself communicates with a connected measurement device for optimizing whitepoint, gradation (gamma) and gray balance.
Monitors with hardware calibration are offered e.g. by
EIZO Graphics Monitors
LaCie Displays
NEC Spectraview
Quato