My goal is to play a console game (e.g. XBOX) while simultaneously
viewing and recording the video.  I have a USB2.0 video capture card
already, but the latency (>500ms) makes gaming impossible.  I need lag
low enough that I can play action games.  I am willing to spend up to
$250 for a hardware/software solution.

The recording format is not important.
The device must be able to input both composite and S-Video.
Perhaps the answer will involve some additional device to complement
my capture card, for example splitting the video and allowing me to
view it in realtime while the device records.  I don't know how to do
this or if this is possible, however.

Thanks!

http://www.leadtek.com.tw/eng/tv_tuner/image/winfast_dv2000_3.jpg

examine this link

you can treat the XBOX like Camcorder, CCD and DVD/VCD Player
so that means you need a tv tuner card that can accept AV Line-In
(which a basic tv tuner card only has a Antenna plug-in

a USB2.0 tv tuner card most likely won't be what you arelooking for, i
suggest a PCI-Tv tuner card like the one mentioned

provided on the website,
http://www.leadtek.com.tw/eng/tv_tuner/overview.asp?lineid=6&pronameid=92,
can also show you the program used to record tv shows and view the AV
Line-in video/audio

step 1:- 
plug XBOX into the AV Line-In
step 2:-
run the program, tune to the right channel
step 3:- 
record the channel

which means basically, if you are playing your XBOX (e.g.Halo) and
recording it, you will see the game and playing the game using your
computer's monitor, while its recording on to whatever format you want
(note: dont record to mpeg-2 as its hard to compress, i suggest
mpeg-1, also note you must have plenty of HDD space for recording
videos depending on how long you record and at what format)

*i used this card as an example because i have one of these and do the
job perfectly, i like recording videos of myself playing supermario
with the super nintendo entertainment system

http://www.geeknewz.com/board/lofiversion/index.php/t268.html

also, this thread is useful for a good read

mesimon,

Thanks a ton for your help.  I couldn't find the DV2000 here in the
US, but I did find the TV2000XP which does exactly what I need.  I am
now recording my game footage in realtime with no noticeable lag!

Hello,
    I suggest a video splitter (HRT has a great one here
http://hallresearch.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=HOS&Product_Code=CSV-3&Category_Code=FEATURED
).  Simply plug your game's output into the splitter, and with extra
cords, hook one output to a monitor and one to your video capture
card.  Play while looking at the monitor and your computer can lag as
much as it likes.
                                   Sam