wireless information theft?

I'm not sure how to correctly title this thread. If you've watched the series of prison break you know what I'm talking about.
There's a few episodes where the characters use a custom device that starts downloading data automatically when its in proximity of anything computer related.
I'm guessing it would have to brute force its way into the target unless its not passworded at all. What I'm asking is how realistic is a device like that?

ideally assuming an unsecured AP?

Wireshark and a few other programs will download anything they can grab with minimal intervention.

Never seen prisonbreak to tell you for sure that the item is feasible but with minimal ingenuity it isnt hard

I'm not at my computer but I'm guessing with software like wireshark and some automation software you could probably develop something that would automatically pick up a signal connect and download pre determined folders.