The Fruity cargo cult has confirmed that the ink, pattern, and saturation of tattoos can block light from the sensor, making it difficult to get reliable readings.

The Tame Apple press has done its best to spin the news claiming that Fitbit's Charge HR suffers from the same problems. Of course Apple is supposed to be a game changer and not make the sorts of mistakes that smaller companies might.

The fault is because the Watch's green LED lights and photodiode sensors penetrate the skin and detect the changes in capillaries and blood vessels. The ink in darker tattoos can impact the absorption of both light and infrared.

So basically if you have a tattoo on your wrist you would be better off buying something else. Apple notes you can connect it to external heart rate monitors over Bluetooth (not that it really helps) but after wasting all your spare cash on am iWatch that is no real help.

Of course most of Apple's target market for the iWatch are the sorts of people who are forbidden by their mums from getting a tattoo.