I’ve always wanted something like Airstash but not using Wifi, instead I’d personally prefer Bluetooth. Air stash is basically a file server which you can carry around with you. You throw in a SD card full of content, power it up and it will serve over wifi the contents to anyone connected over wifi.
Where I think they have gone wrong is tieing it to iphones/ipod touches via a browser interface and using wifi. Bluetooth has a profile for file servicing which works really well once connected and heck if your going to use wifi why not allow a simple samba share instead?
Shame, I would have loved to have had one.