I've just tried the Toshiba FlashAir
8GB SD card in my Minimig (pic controller) and can report from my brief testing that it works well for downloading and uploading* files to the Minimig (whilst it is running) - all via WiFi.
This allows for ADF (or HDF) transfer without having to remove the SD card. The transfers are done via a web interface; you can therefore use any computer,tablet or phone.
The advantage here is that the Minimig can be 'concealed' wherever you please (with wireless kb/mouse and db9 to psx adapter together with a wireless psx controller). It's also nice to save your work to a 'floppy' on the Minimig and then download that adf to a PC (or the other way round). Given the PIC's limitations with directories holding numerous files, it might be better to only have a few files (adf) and update these as required (will test later).
Does the Minimig have the functionality to remember the ADF images it last used (after a full reset/cold boot)?
I'll do some more testing later. I'm happy to try stuff out if anyone has any specific questions.
*Upload functionality is not enabled by default, but is easily achieved by modifying the card's config file. Transfer speed can be slow for large files, but doesn't appear to be an issue for small files like ADF images.