A monk is typically unarmored. Some of their features are based around this. Specifically, Unarmored Defense, Unarmored Movement and Martial Arts explicitly state this.
From Unarmored Defense, PHB pg 78:
Beginning at 1st level, while you are wearing no armor and not wielding a shield, your AC equals 10 + your Dexterity modifier + your Wisdom modifier.
From Martial Arts, PHB pg 78:
You gain the following benefits while you are unarmed or wielding only monk weapons and you aren’t wearing armor or wielding a shield:
From Unarmored Movement, PHB pg 78:
Starting at 2nd level, your speed increases by 10 feet while you are not wearing armor or wielding a shield.
However, I want to know whether other features of the monk class are also implicitly disabled whilst wearing armor. For instance, Flurry of Blows allows you to make two unarmed strikes after taking the Attack action, much the same as Martial Arts allows (although only the one unarmed strike in that case).
There's also Deflect Missiles, which doesn't specifically say that it doesn't work with armor, but the flavour implies it's something that is only possible due to how fast monks can move.
Is there anything I've missed that states that other monk features are disabled whilst wearing armor, or is it only those I've quoted above?