this:

USB 3.0 to HDMI with Audio - Converters - USB - IT PRODUCTS (http://www.siig.com/it-products/usb/converters/usb-3-0-to-hdmi-with-audio.html)

plus this:
Microsoft Surface Tablet For Windows 8 product preview - Tablet - Trusted Reviews (http://www.trustedreviews.com/microsoft-surface-tablet-for-windows-8_Tablet_review)

equals an HD camera monitor/field capture device?????
there is also a microHDMI port, but it seems it is only for output? is that so? and if so, are there workarounds?

It might be that the usb device is also output only...?
Someday one of these tablet makers will realize they have an untapped market by just adding hdmi input or perhaps a thundberbolt port that can be converted to sdi or hdmi.

Yes indeed.
If the Samsung Galaxy Tab 7.7 had a video input, it would make a superb monitor with it's OLED screen.