Higher tech solutions :-):
It requires extra equipment and cost, but any camera that provides live view (or even post-view) video output can be used to drive an external monitor of your choice.
You could use this facility to either drive a monochrome display or a colour display that is able to desaturate the image.
I have not (yet) done this with a DSLR but 9 years ago (!) I had a Minolta 7Hi & A200 (not the DSLR of the same model name) bridge cameras with video output, which I used to drive a small LCD TV to provide "remote viewfinder" capability. This was immensely useful in it=s own right. Being able to optionally view it in monochrome would be a bonus. There are now numerous small LCD modules and screens available which would make this option easy to implement. An LCD on a flying lead is more flexible than even the most capable articulating on-camera displays.
Re separate equipment for "visualising" - a small point and shoot with LCD display, and monochrome display capability as an option would provide this facility. As a bonus, a camera with eg video capabilities assists documentation of your shooting and may even get used to take video of subjects :-). Some (maybe all) of the Sanyo Xacti Video + still cameras have a monochrome mode and record in MPEG video 640 x 480 30 fps or better (later ones are HD), making them a useful companion. Second hand ones here (NZ) cost from about $25 (I bought a C1 this week for $25).