Most analog TV tuner cards include video capture, but not all. Many video capture cards do not include tuners anymore, because ATSC (digital) tuner chips are more expensive than NTSC (analog) tuner chips.
A Slingbox Solo is the ideal tool for you, and can be had for $140 on Amazon.com. It's expensive, but the cool thing about a Slingbox is that you can control your 722 from anywhere in the WORLD. A Slingbox Pro (HD) is more like $240. The Pro also includes an ATSC/ClearQAM tuner, so you can also use it to watch your local TV live...from anywhere in the WORLD.
As a proof of concept, to help you answer the question, "Do I really need/will I really use this?" I'd start with one of these:
[ame=http://www.amazon.com/EasyCap-Capture-Adapter-Editor-Software/dp/B001BWU8US/ref=pd_bbs_sr_2?ie=UTF8&s=electronics&qid=1237486817&sr=8-2]Amazon.com: EasyCap USB 2.0 Video Capture Adapter with Video Editor Software: Electronics[/ame]
You'll also want an appropriate-length
"RCA & S-Video Combo Cable". Follow that link for inexpensive ones (50' for $12.03).
You have to run S-Video and stereo cable from the TV2 output on the 722, so if the 722 is in "Single" mode, both the HDTV and your capture card will display the same stuff. You can also put the 722 in "Dual" mode, and the S-Video cable will carry different stuff than the HDTV output (this is where the 6.3 UHF remote comes in handy).