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Masimo — the company that got the Apple Watch banned — has unveiled its new smartwatch
(www.tomsguide.com)
This is a most excellent place for technology news and articles.
Probably not, most of those sensors work by shining an LED light through the skin and monitoring reflection/scatter as a cheap form of photoplethysmography. Anything capable of absorbing that light, like the pigment used in tattoos, will prevent it from working correctly (at least out of the box, there may be some way to adjust for it but I do not think it would be very accurate).
An infrared sensor could work, depending on the ink type. Unfortunately those are more expensive.