I appreciate the coolness factor, but from a practical perspective I think it would make more sense to go with something that's wearable but more easy to replace, such as a ring or even a piercing.
Piercing seems like a really bad idea unless you can guarantee that no malicious actor will find out about it. Those things hurt when they're ripped out.
The risk of that happening would seem to be equal to or less than the risk of you getting robbed of your credit card, which also carries a risk of physical damage. Normal high-value piercings such as expensive earrings carry a greater risk of theft as they are much easier to covert to money. A wireless payment device requires a second factor for large withdrawals and can easily be blocked.