Is the indirect object pronoun 'le' necessary in this sentence?
 

¿A qué hora le despertó el teléfono a Raquel?

I definitely insert the indirect object pronoun when using the first person and the second person. If it isn't obvious who I'm referencing when I use a third-person IOP, I supply the indirect object. When I supply the indirect object, it isn't a requirement to provide the IOP. That said, I almost always provide BOTH an IOP and an IO in the third person.

Both of the sentences below mean the exact same thing. The redundancy is not frowned upon at all in Spanish.

Despertó el teléfono a Raquel.
Le despertó el teléfono a Raquel.

And, if the now awake Raquel has already been the topic of discussion, you may say:
Le despertó el teléfono.


Now, a little more information:
Escribí una carta. (carta = OD (objeto directo))
I wrote a letter.

La escribí. (la = pronombre de objeto directo)
I wrote it (una carta).

Escribí una carta a Miguel. (a Miguel = OI (objeto indirecto))
I wrote a letter to Michael.

Le escribí. (le = pronombre de objeto indirecto)
I wrote to him (a Miguel).

Se la escribí. (se = le when it's followed by a third-person direct object)
I wrote it (una carta) to him (a Miguel).

Thank you!

Your comments are always so helpful!