1. Whatever the final form of the card(s), the body of the card, what ever is removed from the card, and the compass needle should be glow-in-the-dark. I've read that some such material will glow up to 10 hours after a 30 minute exposure to a light source.
2. I think that more than one card should be used and all sharps should be on just one card. That way any non-sharps card could pass airport security.
3. I have given some thought to something beyond the flosscard. From one end of a more rigidly built card could one could pull out floss or fish line. From the other end one could pull some type of Spectra cord. The cut-off device as used on floss cards should be stronger and sharper. The card could be call the ETS MasterCord.
4. Once I played with the idea of a meds card. Something to hold about 7 meds; say, ibuprofen, Lomotil, Compazine, an antibiotic, etc. Use printed, colored bands on both sides of card to identify each med. On one side, within a particular colored band identify the med, its use, and recommended dosage. On the other side of the card be able to peel away a layer of thin plastic to get to an individual pill without exposing the rest of the meds to the ambient. The core of the card should be a strong, flexible plastic.
5. Build a whistle into one of the cards.