Perceiving through ally without using your action

[Kevingway]

So I know there are ways to link up with allies typically through means of using a spell as some kind of action, but how many ways are there to perceive through the senses of another creature without spending your action? I currently know of one using a Warlock, but warlocks already have Devil's Sight to negate the usefulness of other means of perception 9 times out of 10.

What about ways an ally can "give" their senses?

Any suggestions?