Hi Daniel,
That's certainly a nice-looking solution! Might be a bit of overkill for me though; using a 16Mb SD card that came with my camera, I worked out that if I store 10 bytes of data every minute, I've got over 2.5 YEARS worth of storage capacity...
Just for my curiosity, how would you communicate with this uMMC device? I'm guessing that you'd have to Serial.print() commands like "O 1 R /LOGS/JANUARY/JAN03.LOG{cr}" to it in it's own language?
Thanks!