I like the 32GB swap idea or the Nanoflash idea. Of the possibilities you listed, the Sony hard drive unit makes the most sense. Both of the others add another layer of potential problems. Say the MBP chokes on the footage for some reason…unlikely, but still a possibility. The Internet stream could be prone to any number of disruptions.
I’ve heard mixed reviews of the “Foo” 120K. It uses a USB interface, so I don’t know if it would gradually “fall behind” on you. Then you will probably corrupt a very long clip. Of the people I’ve read using this thing, none of them have mentioned using it for a long, continuous shot. Stopping and starting allows everything to “catch up” to the footage you are sending to the SxS slot, adapter, and hard drive. Rolling continuously doesn’t give it any room for that.
If you really want some security, do the 32GB card swap AND record to NanoFlash from the SDI output of the camera. Redundancy is a shooter’s best friend. You could shoot “SP” mode on the camera’s SxS cards to conserve space, treat them as the backup, and record whatever quality you want to the NanoFlash. Just make sure you’re keeping track of the cards diligently.
Cf