We hire a range of 4K & HD video monitors with HDMI, HD-SDI and composite Video interfaces.
Some come with HDMI loop-thru or HD-SDI loop-thru to allow you to daisy-chain several monitors. this can be useful if you need seprate monitors for camera ops and directors.
Also many monitors now feature LUTs, which allow you to overlay a pre-made grade on to your footage while viewing. This is fantastic as you can see how the shot will look when graded in the final edit - on set and live!