Can a wizard's familiar wake the wizard using its telepathic link?

Question

Suppose I, a wizard, am making camp for the night, and I want to have my owl familiar (obtained via the find familiar spell) keep watch while I sleep and wake me if anyone approaches. Since my familiar and I can communicate telepathically, can my familiar use this mental link to wake me up silently, or will it have to wake me the old-fashioned way, with extremely loud screeching?

Answer 1

The question can be split in two related questions:

1. Can the familiar act on its own? Is it smart enough to do so?
2. Can telepathy wake up someone?

1. Yes

This was already answered here (related here as well). In particular, the spell states

Your familiar acts independently of you, but it always obeys your commands. In combat, it rolls its own initiative and acts on its own turn. A familiar can't attack, but it can take other actions as normal.

From Rubik's answer for the first linked question,

The wizard being unconscious does not affect anything the familiar could already do on its own as it is perfectly capable of independent action. That means that a wizard could have arranged for the familiar to follow actions in the case of the wizard getting knocked out.

So, ultimately, yes, the familiar can try to wake you up.

2. Maybe. Probably not. It's completely up to the DM.

First, let's check XGtE for the Sleeping rules. (Also, related question)

A creature that is naturally sleeping, as opposed to being in a magically or chemically induced sleep, wakes up if it takes any damage or if someone else uses an action to shake or slap the creature awake. A sudden loud noise — such as yelling, thunder, or a ringing bell — also awakens someone that is sleeping naturally.

Telepathy is not loud noise, though. It's up to your DM if they work the same.

Also, check the Alarm spell.

You set an alarm against unwanted intrusion. Choose a door, a window, or an area within range that is no larger than a 20-foot cube. Until the spell ends, an alarm alerts you whenever a tiny or larger creature touches or enters the warded area. When you cast the spell, you can designate creatures that won't set off the alarm. You also choose whether the alarm is mental or audible.

A mental alarm alerts you with a ping in your mind if you are within 1 mile of the warded area. This ping awakens you if you are sleeping.

An audible alarm produces the sound of a hand bell for 10 seconds within 60 feet.

Note that it is explicitly stated that the ping wakes you up. From that, it could be inferred that usually a "mental ping" would not wake you up. Would a telepathic scream wake you up? Maybe.

Ultimately, for balance purposes, this way of using Find Familiar overlaps a little with the utility of Alarm spell, which could be a reason for not allowing it. The Alarm spell is guaranteed, though (doesn't depend on a perception check), so it's not useless even if Find Familiar can be used this way.

Answer 2

Yes, At least in my opinion, they should.

According to the Manual, it says that

While your familiar is within 100 feet of you, you can communicate with it telepathically.

It also says that

Your familiar acts independently of you, but it always obeys your commands. In combat, it rolls its own initiative and acts on its own turn. A familiar can't attack, but it can take other actions as normal.

From what I can see, a familiar should have the ability to take an action to communicate with you, so long they are in range, even if you're asleep.

I would honestly think it's DM dependant though, after all, it can be honestly possible but, some DMs can perhaps say that it shouldn't be/isn't.