Masimo isn't a patent troll.
Yes and no. While they do have products on the market (which means that they don’t qualify under the traditional definition of patent troll), when you look at their complaint, it looks like they’re trying to enforce a patent (an expired one, I might add) on the very idea of a pulse oximeter. Overly broad patents held by a firm with significant market power in captured markets (the highly regulated market for professional grade pulse oximeters, ie for hospitals and the like) weaponizing patents against would be competitors in the consumer space would probably qualify as a patent troll in most people’s eyes.
Masimo claims that Apple wouldn’t have been able to bring the sensor to market without having poached employees, though Masimo doesn’t actually seem to be pursuing any legal action on those grounds or corporate espionage grounds, only the patent grounds. (Also, in California, non-compete and anti-poaching clauses are unenforceable, and both companies are based in California.) Masimo also happens to be a very well connected business politically (good ol’ regulatory capture, no doubt), so, while Apple has a substantially bigger market cap than Masimo, this is hardly David vs Goliath. It’s more like, for lack of a better analogy, Goliath vs Achilles.