Keep in-mind there are alternatives you can use right now, such as BlueTooth to your cell phone, for gigs of data.
I have a little Micro SD/TF card module that was under $2 online, and it's in my current Speeduino case, but I just haven't done anything with it. I saw a member here did "dual-logger" for Speeduino in 2013, but I don't know the status of the code. An alternative is a module like below, with a little Arduino on the back (Pro-Mini?) that simply reads the same serial data stream and saves it to the card module. A standalone add-on logger (similar to OpenLog setups?) that just saves data when you are not connected to Speeduino in other ways.
Just throwing ideas out there.
David
This $2 µSD module with SPI and a $2 Pro Mini or Nano might make a good auto-logging setup that isn't mixed in Speeduino code?:
uSD_module.png (83.4 KiB) Viewed 13795 times