I think it's fantastic. I don't typically hand out a physical business card often. So the recipient would be someone that I would feel would generally find the project exciting and intriguing, and it provides a great conversation piece. It's simple enough to discuss it briefly and mention that for any security-conscious individuals, they can check out the GitHub that's stated on the card and see the code and still have the same insight if not more than if they had just plugged in the device. For anyone else, the information they need from a business card is all still nicely stated, in a design that's enticing even without functionality. The production cost is easy to justify with the chance of achieving whatever your goal may be, whether it be securing a job offer or generating new business.