That one is exactly the card - for me it did a full cards worth of mlv with sound, 1920x1080x25, without dropping frames or any anomalies. I would say that in both of my 5d3's it's a bit faster than the 256G/Extreme Pro. I will order the 128G version also for testing.
For capacity the best card is 256G Sandisk Extreme Pro, that does 1920x1080@25 with 5d3, but not 30 (at least mine does not). Cheapest RELIABLE sandisk-option for me seems to be Sandisk Extreme 120MB/s - i've got one 64G version and it does well with 1920x1080@25. I did like Komputerbay before, but with the long waiting period for exchange if the card is faulty the sandisk seems like a better option. Pic from ML:
Just a bit offtopic: Are there any drawbacks, when I would like to use a tablet with 2.5K resolution for the same purpose - monitoring.
I was thinking of Onda v973 with retina display, as it's the cheapest of it's kind, offering great image + usb port. Would it make sense to use it, or the similarly priced "field monitors" with lower resolution are better at this ?