Way of the Hummingbird

Monks of the Way of the Hummingbird follow the mantra that even water can cut through solid stone if it moves fast enough. Sharpening their mind, they learn lightning fast reflexes and learn to move and hit like a blur. Masters of this practice are some of the fastest fighters to exist, both physically and mentally. 

Credit to u/dragonmorg for the original idea

Reflexive Counter

Beginning at 3rd level, your sharp mind and quick foe analysis allow you to strike back at your foes when they attack and leave an opening. When a creature within 5 feet of you misses you with an attack, you can use your reaction to make an unarmed strike against the creature.

In addition, you can use your reaction even if you are surprised.

Improved Unarmoured Movement

Starting at 3rd level, you learn to move at lightning speed. Whilst you're not wearing armour or carrying a shield, your speed increases by 10 feet. You gain an additional 5 feet of movement at levels 6 and 17, along with an additional 10 feet at level 11.

Eyes of the Hummingbird

At 6th level, your mind has quickened so much you can harness your ki to slow the world down for you momentarily. If you have already spent your reaction, you can spend 1 ki point to gain an additional reaction. You can only gain an additional reaction once per turn.

Additionally, when you use your Reflexive Counter feature, you can move up to 10 feet as part of the reaction attack. Opportunities attack triggered by this movement have disadvantage.

Mind of the Hummingbird

At 6th level, your mind has sped up and you can process information much faster. When you make an Intelligence (Investigation) or a Wisdom (Perception) check, you are considered to have Expertise in the skill, provided you don't already have it and you don't have disadvantage on the check. 

Additionally, the time taken to read a book, tome or other piece of writing and learn a proficiency in a tool, language or skill is halved.

Extra Attack

Beginning at 11th level, you can attack three times, instead of twice, whenever you take the Attack action on your turn.

Blur of the Opal Step

At 17th level, you gain the ability to briefly increase your body's natural metabolism and reflexes to unbelievable speeds. As an action, you can spend 4 ki points and cast haste, without requiring verbal, semantic or material components. When you cast haste in this way, you can only cast it on yourself, it requires no concentration and your jump distance is tripled for the duration.