We last saw the Bigstream device back at CES earlier this year, but it's out and available now and I got to plug one in and see how it worked on my home television. The result? It worked out OK, with a couple of issues.
The biggest issue is compatibility with apps, because setup is very straightforward. The device comes with two pieces -- a receiver with a power cord and video cable that goes to any standard RCA composite video connection, and a wireless transmitter that plugs directly into your iPhone (or iPod touch, or iPad, though I did all of my testing on an iPhone 4). Turn both on (unfortunately, both have to be manually powered on, though presumably the receiver could stay on) and set them to the same of three channels, and then any video out signal from your iDevice will go straight to the TV. Note that the only option for plugging in to the TV is currently the RCA cable -- HDMI and S-Video aren't available.
Unfortunately, most apps that I tried simply aren't compatible, and though Bigstream does have a list of compatible apps on their page, there are a few that still didn't work for me.
Specifically I couldn't get The Incident to work -- it's listed as compatible for video out on the iPhone 4, but all I could find was an option to use it as a controller when connected to an iPad.
Strange, especially since that's the actual app that we saw at Bigstream's booth at CES. (Update: Bigstream tells me that the display at CES was actually of an iPad sending video out to the device, using an iPhone as a controller. I didn't actually try that setup, so presumably it does work, just not directly from the iPhone itself.)
I did get the YouTube app to work pretty well, though the quality was off, probably because YouTube quality isn't that great to begin with. And the Netflix app worked particularly well -- there were a few audio and video glitches during setup (the transmitter's dock connection can cause some issues if jiggled around), but once the streaming ran over WiFi, the Netflix picture looked pretty good, and the whole rig ran great.
In other words, Bigstream's compatibility presents some issues -- you can't just load up your favorite game or app and stream it right off to the television, unless you can somehow convince your favorite developer to stream the video out. But fortunately, the apps that Bigstream is compatible with do have some promise, and give the unit a lot of functionality already.
For example, if you're on the road often and want to watch Netflix on something a little bigger than your iPhone's screen, I can see carrying the Bigstream unit around with you, plugging it in to a hotel room TV, and then using it wherever you go. Likewise, though I wasn't able to try any of this software specifically, it seems like it would work well for presentations, allowing you to plug in to any television with an extra power cord and RCA hookup, and put whatever you need on a larger viewscreen (though of course I'd recommend you test it first to make sure everything works). Keynote, in particular, should be well-suited to this task.
As for home use, Bigstream would work (maybe if you don't already have a device plugged in to your television to run Netflix and other streaming video apps), but it's a hacky way to implement functionality that you could get with cables from Apple. If all you want is Netflix and YouTube on your TV screen, an Apple TV will give you that, and in even better resolution. Unless there's an app that you specifically need to use, and it happens to be compatible with Bigstream's device, there's not really much to recommend you running video out of your iOS device rather than just a dedicated box for that at home.
Bigstream's unit costs $99, so it's a fairly significant investment for what it is. It definitely works as advertised -- if you need to send video out from your compatible iPhone app to any television just by hooking up a few cables, Bigstream pulls that off well and with a minimum of fuss. Just be sure you know ahead of time what you're trying to do it with it; the system seems to work better as a portable device built for specific uses rather than a general household tool.