Permanently using an SD card for extra storage?

The 13" has that handy SD Card slot on the side. Does anyone have an SD card permanently in their MBA for extra storage? I'm considering getting one to avoid using my external HD when I end up with more things on my computer.

I've often bought the wrong type of SD Card (microsd, minisd, sd, all the different kinds) though. What should I be looking for, and what price do they run at?

 

Thanks so much!

(Also I tried searching, but the search is pretty messy for me. Sorry for posting something that's been answered!)

 

I went straight to the end as I usually do to get the latest info in a thread, and saw it. I'm going to wait for the product to be commercially available, since the kickstarter has ended. I'm hoping shipping won't be too expensive to South Korea since I'm moving in a heartbeat