There are expensive 3D monitors available. However, I am cheap. Hence, this thread is a list of somewhat cheaper options.

If you are using a dual camera setup - you need to sync the 2x HDMI or HD-SDI signals into a single HDMI 1.4a signal.

Options are Matrox mc-100 or AJA Hi5-3D ~ 500/- USD

The cheapest monitoring option is the Sony HMZ-T2 or Sony HMZ-T3 Don't get the T1 as its too bulky.

Hi5-3D has an anaglyph option that will allow use of a 2d monitor with the red-green glasses. The user manual lists the method for selecting anaglyph on pages 9 and 10: http://www.aja.com/pdf/support/manuals_conv/AJA_manual_Hi5-3D.pdf These go for about $500 USD and consume about 5 watts. It also supports full frame-pack as well as SxS and TxB squeezing output modes.

The most portable option for a native 1080p monitor seems to be TVLogic http://www.tvlogic.tv/Monitors/M_Spec.asp?sidx=49

There are a number of tablets and PMPs by Gadmei - but none of these offer an HDMI input.

If you know of a cheap-ish display, PMP (less than 1K) that offers 3d HDMI input (either single 1.4a HDMI or dual HDMI) do post about it.