This only meets part of your requirements, since it does put a humanoid in the line of fire (though it doesn't have to be a friendly humanoid).
It's maybe not RAI, but a Warlock with the Gaze of Two Minds Eldritch Invocation can see through the eyes of a creature on another plane for a single round.
You can use your action to touch a willing humanoid and perceive through its senses until the end of your next turn.
The restriction on seeing across planes is only on the renewal clause:
As long as the creature is on the same plane of existence as you, you can use your action on subsequent turns to maintain this connection...
You have to do the following:
- Gaze through the eyes of a humanoid on your turn
- Send the humanoid to the plane of your choosing using Gate or whatever on their turn.
- See through their eyes until your next turn.
You can get a little more out of this by using a Fighter as the humanoid you are looking through, and having them Action Surge to get an action on the far side of the portal.