Way of the Unsighted

Through some means or another, monks following the Way of Unsighted have found themselves blind. However this far from diminishes their capabilities; with no eyesight to rely on these monks channel their ki into their other senses, navigating the world through hyper-enhanced hearing, taste, smell, touch, and a myriad of other acute sensory experiences. 

Perhaps an accident destroyed your eyesight but enhanced your other senses as a result, perhaps you are a member of species that are born blind but have other extra senses, or perhaps you attempted to learn these techniques while sighted and had to sacrifice your eyes to maximise the enhancement of your other senses. Whatever the case, these monks' enhanced senses allow them to detect creatures that are otherwise unseen, discern illusions and lies, pick up actions and conversation from afar, and react to danger almost before it is upon them. However these monks cannot be careless - their enhanced senses can also exploited by intelligent foes who know how to overwhelm them.

World on Fire

When you choose this tradition at 3rd level your enhanced senses have fully developed and granted you special abilities, giving you a unique perception -- a world on fire.

You gain Blindsight and Tremorsense out to a number of feet equal to 10 x your proficiency bonus, but become vulnerable to thunder damage and lose your sense of sight. You do not suffer the Blinded condition (in fact you are immune to it) but do have disadvantage on attack rolls against targets outside the range of your special senses and automatically fail any checks that rely on sight (though in turn are immune to effects that rely on sight such as the Hypnotic Pattern spell and most illusions). If you are unable to hear such as with the Deafened condition, then you have disadvantage on attack rolls and attack rolls against you have advantage but you can still pinpoint the location of creatures with your tremor sense as long as you are in contact with the same surface or substance as them. If you cannot detect a creature with your tremor sense, then you can make a Wisdom (Perception) check to discern its location with other senses such as smell or disturbances in the air even if it is behind Total Cover. The DC for this check is equal to 10 plus the creature's dexterity score. If the creature has proficiency in Stealth then add its proficiency bonus to the DC for this check. If you succeed, you are aware of the creature's location for 1 minute as long as it remains within 30ft unless it successfully Hides from you, after which you must succeed on this check again to locate it.

Additionally, you can spend 1 Ki point to detect magical presences for 10 minutes as per the Detect Magic spell. Rather than "seeing" the magical auras, you sense them similarly to Blindsight. 

Note that the DM may determine that certain obstacles disrupt your Blindsight, such as busy crowds or persistent loud noises. In these cases, the DM can call for Wisdom (Perception) checks to pinpoint specific creatures, conversations, etc., determining the DC as appropriate to the difficulty.

Distant Detection

Also by 3rd level, your senses are acute enough to pick up on subtle stimuli like footsteps, whispers and breathing even from a distance.

You can hear footsteps and conversation as quiet as whispers from up to 100ft away (even through walls), and loud conversation or yelling up to 300ft away. This sense of hearing gives you a rough layout of your surroundings up to 300ft around you. Up to that range you can discern the layout of streets and buildings, and within 100ft can discern interiors through walls. The DM determines the extent of detail you learn from a distance but at minimum you know the arrangement of rooms and notable uncovered objects within including numbers of creatures.

Additionally, as a bonus action you can spend 2 Ki Points to focus and learn the following information within the range of your special senses:

• the location and shape of any concealed objects, including those being worn or carried, such as a gemstone in a safe, a key inside a pocket, or what equipment a creature is carrying that isn't inside a bag of holding or similarly extraplanarly concealed
• what substances a creature has consumed within the last 8 hours, such as meals, potions or poisons. As such, you also detect the presence and location of poisons and disease though cannot identify them if they are unfamiliar to you
• if a creature or object has been in physical contact with another creature within the last hour. If that creature would have a particularly unique or powerful aroma then you can detect them from up to 8 hours
• where a creature or object has been within the 8 hours, such as a tavern, stables, or a particular person's house. If that location would have a particularly unique or powerful aroma then you can detect it from up to 24 hours. This also works in reverse — you can tell if an object or person has been at a location you are at within 8 hours, or 24 hours with particularly powerful or identifiable aromas.

Note that a DM will likely only give you unique information -- i.e. things that other sighted creatures could not see. For all intents and purposes, you do not need to spend Ki points to learn things that sighted creatures would already be aware of as you can discern the same information through other senses (unless it requires sight such as printed text, or light or colour information). Spending Ki points in this way should grant you additional information that other players have missed or could not work out. However also note that this ability is not magical divination — it relies on physical stimuli and so can potentially be fooled or misinterpreted at your DM’s discretion, though this should be rare.

Finally, within the range of your special senses, you can discern a creature's body language and gestures (such as nodding, waving, how they are posed) but cannot discern more detailed information such as their facial expression or direction of gaze.

Ear for Deceit

By 6th level, your senses have become so acute that you can hear a creature’s heartbeat and feel minute changes in their body temperature, among other subtle emotional indicators.

You have advantage on Wisdom (Insight) checks as well as Wisdom (Perception) checks that do not require sight. If you already have proficiency, you gain expertise instead.

Additionally, as an action you can spend 2 ki points to learn if any creatures within your special senses are lying for 10 minutes. The creatures are not compelled to tell the truth, but by reading their heartbeats you can tell if they are lying or omitting information. A creature that is aware you can read its heartbeat can perform a Wisdom saving throw against your Ki save DC to keep calm, fooling your senses. A DM does not have to disclose if a creature is making this save or if they succeed or fail. When you perform this action, you are also aware of a creature’s emotional state for the duration, though again a success on the Wisdom save fools your senses into detecting them as being calm. Creatures that do not have a heartbeat (such as constructs and most undead) are immune to this effect, though using it on them reveals their heartbeat-less nature to you.

Pre-ceptive

Also by 6th level, your enhanced senses let you pick up on danger almost before it occurs. While not deafened, you have advantage on initiative and cannot be surprised.

Additionally, you have advantage on Dexterity saving throws while not deafened or incapacitated.

Magi-sense

By 11th level, your senses have even become attuned to the subtle but ever-present magic that permeates all of reality. You are permanently under the effects of the Detect Magic spell, sensing magical auras akin to blindsight rather than seeing, out to the range of your special senses.

Additionally, your acute magical sense allows you to immediately tell when arcane energy is accumulating in the process of producing a spell. When a creature within 5ft of you begins casting a spell, you can spend your reaction to make a melee attack against it. After the damage is dealt, the target must then succeed on a concentration check (as if their concentration on a spell had been interrupted). On a failure, the spell is not cast and the spell slot/usage is wasted. Alternatively, you can spend 1 Ki point when you make this attack to attempt a stunning strike as normal. If the creature is successfully stunned, the casting of the spell is interrupted and the spell slot/usage is wasted along with the usual effects of being stunned.

Extrasensory

By 17th level, your senses have become so heightened that they transcend planes of existence.

You gain Truesense out to a number of feet equal to 10 x your proficiency bonus. Similar to Truesight, this special sense allows you to be aware of creatures on the ethereal plane. You cannot “see” them due to your lack of sight, but you can sense them in all the same ways as with your Blindsight and Tremorsense, though are unable to hear, feel, or otherwise physically interact with them as usual. This sense also allows you to discern when a creature is not in their true form and what creature type that true form is (such as human, fey, dragon, etc.) by picking up on the subtle lingering magic of transformation, however it does not reveal the appearance of that true form to you.

Additionally, the first time you hit with an attack on your turn, you can spend 2 Ki points to assault the target’s senses by overwhelming them with your Ki. For 1 minute, all of your attacks against the target deal one additional martial arts die of Psychic damage. You may spend additional Ki points to deal extra damage for the duration when applying this effect. For every 2 additional Ki points you spend (up to a maximum equal to your proficiency bonus), you deal one additional martial arts die of Psychic damage with each attack. A creature must have at least one sense to be targeted with this effect.