Well, no sooner did I say that, I actually got it to work. Using this
EasyCap, with the UTV007 chipset as advertised. Firstly, to get the RPi to drive the LEDs through the Arduino, it appears you set the following from the Hardware tab in HyperCon:
Type: Adalight (maybe other options work) and
Output: /dev/ttyACM0
I had one other issue personally, that you may or may not have had. I'm using 228 LEDs, and apparently that is too many for the internal memory of the Arduino Uno. I changed my sketch to 150 LEDs and bam, everything started working. Only problem now that I see is that it is on all the time, and I'd like the ability to switch off. The off button in the Android app only appears to control the colorwheel selection, then it goes back to ambilight.
Yea, this was my exact same issue. I never knew that I had to use Adalight as the Type. And regarding the grabber, the chipset inside mine isn't UTV007.
Not sure about the LED's while using the ambilight tho, I'm haven't got my grabber yet so I can't say if it works well yet, however with about 200 LEDs, the Hyperion app color and effects works perfectly fine. Now that you mention about being unable to turn it off, I might consider adding a switch as well.