There are certainly devices available which can take any of a range of video input signals and display them on a VGA (xGA; whatever) monitor. Price might start at $80 plus shipping, and on up for additional functionality.
I use a "COMP2VGATV" from StarTech.com (via CDW.ca), which delivers a VGA signal from a Composite Video input (or S-Video, or coax with limited tuning). I don't recall having tried it specifically with my LCD monitor, but it should get the job done.
There are also High Def and other versions available (e.g. on the CDW website, select "Hardware", then "Audio/Video", then "Video Adapters", then "TV Tuners/Converters/Adapters", to see a selection; scan through the list to weed out the standalone devices from the PC-based devices).