Trying to find a way to take component video and audio output from a device, and preview it on-screen in a window. We don't need recording or encoding capabilities, but we would like as low latency as possible. This would allow us to hook up things like a TiVo or game console and play it in a window of our PC without having to dedicate an entire monitor.
I would highly recommend the Elgato line of capture hardware as they are reasonably priced, well supported, come with the software you need and have been in the business for quite some time.
Even for some prosumer applications, Elgato hardware is good enough for the job as some input sources are not going to be improved by spending $2000 on hardware that can do impressive amounts of A/D conversion and fancy time sync olympics.
You could go cheaper on the hardware (especially if you only need composite instead of component input), but my experience is if you know exactly what you're doing - you already can judge what cheap thing you can press into service and what is a waste of your time. I'd buy from a retailer that has a nice return policy or can make sure you buy the appropriate package.
Though this speaks more to a digital signal (more on that in a second):
Some laptops have HDMI Input in addition to HDMI output (the Alienware M17X is one). This would allow low-latency video to be seen in a window on the laptop screen.
- Macbooks do not support this.
- Mac towers can install HDMI capture cards, with caveats that I'm sure you've already researched. The BlackMagic Intensity line seems to be a front runner for low-latency, but it's not a product I've tested.
In all cases where you want to connect a component (or any analog) video source to a computer, you will introduce latency because it always has to be encoded.
Edit: Since the Intensity line now supports thunderbolt, a thunderbolt-equipped macbook may allow for low-latency display.