You're missing a very important limiting factor: battery life. You can't fit a lot of battery in the space of a credit card, and you can't exactly count on unwitting carriers to properly recharge and maintain them.

Given those constraints, practical applications would be severely limited. As the article mentions, it's probably undercover personnel who are carrying these. The power budget would likely rule out remote access or remote streaming. I'm guessing these credit card snitches are little more than local audio/video recorders with very limited run time.