You have the one SD card with many keys inside (instead of many SD cards with just one key). You can actually see this in the video produced by the creator of this system: http://www.youtube.com/watch?v=ZR8gz0uVBHk&feature=youtu.be
This idea is very close to my proposed conception. Actually this idea can be completed with NFC technology cos the speed of pairing and connection of NFC is extremely high.
The main idea is to separate some amount of bitcoins, store and transfer keys.
I didn't understood a few things. How recipient can be sure that the payer didn't make (or someone else) the duplicate of the key?
And can the recipient get that key without been proceed this transaction online?
And can the recipient transfer key which he got from the payer to another recipient ? without been proceed and verified this keys online first
can it be multiply offline transactions?
like it's shown in 4b situation