Ok, so you got your DSLR and fancy new Rode VideoMic Pro with +20db feature. If you've got AGC on the T2i (without ML) or Canon 7D, then you need a way to disable AGC. Or maybe you don't? Maybe you've got a Canon 5D Mark II or 60D with Manual audio levels - no AGC to worry about. You're still short of a way to monitor the audio levels via headphones.
There's been different ways of trying to get clean audio into your camera, but it normally came at a hefty price. Here's where this new JuicedLink DS214 comes in. Just recently announced as available for purchase for under $145 bucks, this little black box provides all the missing features of running a stereo jacked microphone into your camera. The DS214 provides you with Audio meters, a Low-Noise Preamp, Headphone monitoring, and even AGC Disable if needed (everything that sucks for a DSLR). Ok, yes you can use an MP3 player with constant tone to 'tame' the AGC, but still no way to adjust levels from the Mic, or give a little low-noise preamp boost to the signal. Any way you cut it, this thing was thought out to include all the different 'workarounds'. For the price and convenience, it can't be beat.
This version doesn't have inputs to support XLR Microphones, but there's a swamping new audience using the Rode VideoMic Pro that sure could use something like this. For XLR phantom power you'll want to check out the DT454. Only 1 stereo input? The DS214 also has seperate L/R potentiometers which makes it possible to run a splitter to two different mics and capture mono on each channel.
As of now the new JuicedLink DS214 is only available on the JL site with a bunch of information which I suggest you checkout to see if this will work for you. There's also some different Audio Samples from a variety of possible Audio setups with the Rode Mic + Zoom H4n you can listen to.