Apple Watch Hates Your Tattoos
If you've been planning to buy an Apple Watch, but you've got a tattoo right where the back of the watch would rest on your wrist, you may want to think twice: dark tattoos can cause it to malfunction.
This is because it detects (for security and other reasons) when it is being worn by measuring light absorption through the skin. A dark tattoo can confuse the Watch into believing it has been removed from your person.
Quite how such an elementary and predictable issue made it past QC in Cupertino we may never know, though perhaps Bendgate was an early sign that their standards have taken a back seat.
h/t +Alan Stainer