There are converters that output SDI available from Convergent Design, Black Magic, and Miranda, among others. These are desirable for outputting uncompressed HD/SD. You'll also need a very high end, top quality computer, plus the very high cost of an SDI/Component HD monitor.
You'll do OK using a second computer monitor, or if you want the best of both worlds, I'd recommend one of the Luma series monitors from Sony, as they're tuned for broadcast, and the closest thing to CRT you'll find. FWIW, attendees of the "I Want My HDV" tour get a sizeable rebate coupon from Sony for these monitors.